if the show is serial, 3 is usually all it needs and it will go downhill beyond it. 5 is like the max for REALLY great shows. I know some stretch longer and they're fine, but if you want true wire to wire masterpiece, going longer than 5 is likely to result in something short of that

the MAJORITY of shows would probably just be better served as limited series for the sake of their story that don't really have much legs and will end up wasting a lot of time with side quests that get in the way of the overarching narratives, but the economics of it all say "popular show -> make more seasons" and creatives say "more seasons -> more money for me"

If it's like a sitcom or police procedural or whatever else is purely episodic without much in the way of overarching narrative, then sure, go nuts, do whatever you want.