I don’t believe there was any rule stating this. Some embassies may have stated that was the case but it’s a 5 year visa. You have to use it within that time.
There is no technical expiration date for a TM30 although there is a non compulsory field for “check out date” that some offices could say is the validity date.
However even if you haven’t left Thailand, but stayed in a hotel or hospital somewhere that could override your address in the system.
Some offices won’t care, some will only consider the existing record as the current address on file.
Advising people that they can “use any office” is just wrong. I don’t give a shit about your thoughts but I do give a shit about advising people correctly.
The OP has a retirement extension he was asking about getting that stamp moved to a new passport. For general stuff like a tourist or visa exempt extension then you can use any office. For the OP it’s a different story.
You had a retirement extension and you got a new passport? You randomly chose one of the 80 plus offices around the country and got them to change the stamp over?