After more than a year of unplanned hiatus (^_^;) I thought this might be something useful to write about --- how to neatly migrate EZ-Link-related facilities when switching cards. Applicable to Singapore residents only.
Disclaimer: I am not affiliated with any of the companies whose products are mentioned here. I am just an opportunistic user in constant lookout for extra benefits (i.e., a stereotypical Singaporean).
Background and Overview
My POSB Everyday credit card, which doubles as my EZ-Link card, expired recently. In my understanding, the EZ-Link purse should still be usable after the credit card expiry (it has a different expiry date), but it was better for convenience and security to simply switch all usage to the replacement card (hereafter called "new card") and destroy the expired card ("old card").
The switch, however, involves changes to a few EZ-Link-related functions I have on the card. I've had to chart those things to figure out an optimal order of execution, so I decide to document the steps. After all, the new credit card will expire in 5 years and this will become relevant to me again, although some functions might not survive until then.
The following is structured by functionality, while action items are numbered globally in the order of execution. Hence, there will be numbering jumps within a section. The sequencing is not really strict; some steps can be done in a different order or in parallel. The general direction is towards preparing the new card for use and retiring the old card. Actual dependencies are noted in explanations and illustrated in the summary at the end of this post.
EZ-Link Activate 
I use this for transaction tracking / statistics and the free card insurance. I actually registered hoping to check card values off-site*, but that wasn't its intended function, as transactions are not immediately reflected. There are supposedly merchant offers and discounts but I've seen none of them so far.
* The tool for that is EZ-Online, but you'll need your own card reader.
(1) Add the new card to the Activate account 
This step is not critical but it is the easiest to do, and it ensures all transactions continue to be tracked. Up to 3 cards can be registered in one account, so it is not necessary to remove the old card at the same time.
(10) Remove the old card from the Activate account
Statistics are up to past 3 months only, so Activate will have nothing useful on the old card when it has been retired for 3 months. It is not really necessary to remove until you need the slot to register another card, but it's a good housekeeping practice, I suppose. One less string of digits to compare in the event you forget which card is which.
EZ-Reload (Auto Top-Up)
I use the auto top-up facility charged to POSB Everyday credit card, because the current rebate for EZ-Reload on that card (2% --- $1 for each $50 top-up) outweighs the top-up fee (25c). The fee itself has been waived for some time now, "until further notice".
At the moment there are cards with higher rebate rate, but I don't want to get one more card just for this, when I can use Everyday for other payments with pretty good rebates too.
To clarify, it is not necessary to use the credit card itself as the EZ-Link card in your travels. Auto top-up of any EZ-Link card will earn the rebate when charged to the credit card. I use the same card just to keep my wallet slim.
(2) Apply for EZ-Reload on the new card
The credit card number (which identifies the credit account) remains the same upon replacement, but the physical card will be embedded with a different CEPAS Card Application Number (CAN), which identifies the EZ-Link purse. It is the purse that EZ-Reload is linked to, so the new CAN needs to be registered for EZ-Reload.
Clearly, the registration should specify the new credit card to charge to. The difference is only in the card expiry date, as no other information is requested. In fact, while the old card was still linked to EZ-Reload, the EZ-Reload system noticed the approaching expiry date and sent me a request to update the credit card information.
As specified, wait for confirmation within 5 working days after registration, before the EZ-Reload facility can be activated.
(3) Activate EZ-Reload on the new card @ GTM
Follow the instruction in the confirmation e-mail to activate EZ-Reload at a General Ticketing Machine (GTM) located at MRT stations.
If you do not plan to use the card for travel before this step (which is my assumption here), there is no need to manually top it up. The EZ-Reload facility will kick off on the first usage, when the EZ-Link purse contains exactly zero value.
(7) Terminate EZ-Reload on the old card @ TransitLink Ticket Office
According to TransitLink staff, the remaining value in the old card's EZ-Link purse cannot be refunded if the EZ-Reload facility is active. (As a refund will zero the purse, I suppose it will confuse the auto top-up system?) Go to a TransitLink Ticket Office to request termination of the facility. Cash refund can be requested (also at a Ticket Office) after 6 working days.
Travel Smart Rewards (TSR)
I think of this as some sort of rebate scheme for MRT travels. This MoneySmart article is a good tutorial on this. TSR's official FAQ with the advanced details is accessible only from within an account, which means one has to create an account first.
(4) Claim TSR winnings that are marked for crediting to the old card, if any @ AVM
If there is any winning with the status "Will pay to travel card xxxx" (where xxxx is the CAN of the old card), bring the old card to an Add Value Machine (AVM) to claim it*. We generally want the amount to already be in the EZ-Link purse for refund at one go, in a later step.
* The claim function is under "INSINC Rewards" from the AVM main menu, INSINC being the former name of TSR, apparently. I had some confusion in my first claim attempt (as a late entree to this game), so I thought I'd mention it here.
Winnings with "Pending" status will remain in the TSR account, so not to worry. After the active card is replaced (in the next step), future crediting will be to the new card.
(5) Register the new card in the TSR account
Right before starting to use the new card, register the CAN of the new card at the Settings page ("Request a new card number"). While it takes time to verify the new card, travels made on the card will be counted from the point of request, so start using the new card on the first weekday after the switch (since weekend travels do not earn points anyway).
Do not cancel the old card in the account (the button for that is appropriately in warning red). If it is cancelled, travels on that card that have occurred but not yet reflected (it takes several days) will not earn points. The old card will automatically be removed when the new card has been verified.
As far as I can infer, there is no harm bumping out the old card (in step 5) while it still has unclaimed winnings (before step 4); the winnings will remain there waiting to be claimed, as long as you retain the physical card to do that. But I prefer to make a clean break and do them in this order.
Any Other Business
(6) Put the new card to actual use
Test the new card for travelling and all other things you use it for, to make sure everything works as before.
(8) Get a cash refund of the remaining value in the old card @ TransitLink Ticket Office
About 6 working days after terminating the EZ-Reload facility, go to a TransitLink Ticket Office to request a cash refund of the remaining value in the old card's EZ-Link purse. In my experience, the staff asked to see my new card before she proceeded, I'm not sure why.
I read from DBS Live Fresh card FAQ that there is an option for "deferred refund" to the credit card tied to the EZ-Reload facility, instead of cash refund, but for some reason it wasn't applicable to my case. The TransitLink staff strictly told me to terminate the EZ-Reload facility first, and get a cash refund 6 working days afterwards.
The same FAQ also mentions that the TransitLink staff will destroy the old card after refund, but in my case, the staff returned the card to me. To be very safe, I would still suggest doing this after you are sure you do not need the old card anymore.
(9) Destroy the old card
As banks always advise, cut up the old card when you have no more use for it. Here's a tip on properly cutting up and disposing of old credit cards.
Summary
