I was about to go to sleep, but I can reply to this...
Generally speaking, casinos sometimes use their own tools or external software to check for potential bonus abusers and multiple account holders. These tools can simply check your name, address, phone number, IP address etc.
Then the next account check is usually done manually once you request your 1st withdrawal in the casino. If the check is passed, then it's usually valid until one of the following happens: your ID expires, your card expires, you use a new payment method that hasn't been verified before.
There are also moments when your account can get "flagged" for some reason so the casino requests additional check (selfie with ID, verification call etc.). The account can get flagged even if you don't do anything wrong, but let's say there's a new player in the casino who uses the same name as yours, the same IP address, same device etc. Then the casino wants to be 100% sure that these 2 persons using "the same IP, device, name or anything else" are 2 different persons.
Basically if you play, your ID and card are valid and you don't use any other payment methods, then there's a high possibility that you shouldn't need to verify your account again during the same year.
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