legend has it that they wrapped up everything beautifully and then got told they had to make another season
I just started the second season, but yeah this was pretty common for big shows. Same thing happened to Trailer Park Boys and Curb Your Enthusiasm. They had their "last" seasons, then got revived out of nowhere.
You should be good up to season 3 or 4 (I can't remember which one but one of those was the planned last one) and then after that it gets "interesting" (not entirely a dumpster fire but you could be forgiven for giving up).