Are we talking US Seasons (22 Episodes around 45 minutes) of UK/Netflix Seasons (6-10 one hour episodes).
Because most shows don't even deserve four US Seasons, IMHO. I think four UK seasons is normally okay to tell most stories.
I'm focusing of shows that tell stories, as I don't think the OP was thinking about comedy panel shows or quizzes. I'm also more interested in fantasy shows which inspire RPGs than various cop/hospital/school dramas based on real life.
Generally shows that are showing episodic rather than serials telling a major story over a season, tend to run longer. Episodic stuff normally features on the characters with how they react to different short story events each week. Serials are more focused on the story arch which can normally wrapped up over a few seasons, the characters develop but serve the story once the story is over and the characters have changed there often isn't a reason to follow them anymore. In episodic stuff the characters rarely change, they stick with their archetype so you can keep putting in them in different situations, and short stories, if people like (or even hate so long as they want to watch them) the characters they just keep going and going.
There are plenty of shows that seem to combine the two with generally episodic nature but with a season spanning plot now. They are still basically episodic in nature so the character don't change significantly.
Soaps, hospital and cop drama's run and run as the writers have plenty of source material with it being based on real life. Fantasy stuff like Buffy, Star Trek, etc. have a harder time for the writers to come up with stuff original and engaging, so can go stale after a few seasons. These fantasy dramas are also the ones that tend to blend the serial with episodic nature, so once they have done the serial plot they seem to reach a logical conclusion. Battlestar Gallactica for example, the crew had an overall goal, once the Cylon problem was resolved story was going to be over and how long can you drag that story out before people get bored of waiting for a resolution.
Doctor Who is an odd one it can refresh itself by changing the cast/writers/directors regularly, and has the whole of time and space to play in, while there are bad episodes and even bad seasons, the show can always find new content. There are over arching stories but they tend to end with the regeneration of the Doctor, and kicks of a new story arch with a whole new cast. This has given it legs other fantasy dramas don't seem to have, the exception being Star Trek. Star Trek is pretty much a workplace soap but set in future and space, so it can stay fresh changing the background to a whole new planet each week.
I would have liked to see The Expanse continue as it still has barely touched on what's on the planets on the far side of the gate, but I think that changed the nature of the show as well as it became less about the Mars/Belter/Earth dynamic.