I've been doing a lot of reading lately, and one thing I have almost universally discovered, is that most people tend to shift gradually from love of a show to hatred as time goes by. This isn't to say that people don't enjoy or watch the show after then, but they don't like it as much as before. For some reason, this "divide" usually happens after season 5. Why is this? Let's look:
Season 1 is all about establishment. A lot of shows never make it past season 1, and those are mostly shows with a lot of questions and backstories. In general, it takes the entire season to establish some aspects of the characters, as well as throw in some good conflict (Especially if it is a backstory conflict, it gives more "setting up" in another episode). In general, by the end of the first season, not all the questions have been answered, but you at least have a firm grounding of what each character "does."
Seasons 2 and 3 serve roughly the same purpose. In these seasons, characters and settings are defined, as per season 1. This is where things tend to start changing, and developments occur. However, there are still plenty of fresh ideas for the writers, and it's not a big issue. Usually, the stories still make sense and they're engaging. Seasons 2 and 3 are usually the most liked out of all the seasons of a television show, mostly because they're the seasons where people grow more attached to the characters as they grow and change.
Season 4 is where writers tend to start running out of ideas. This may be because they didn't expect to go 4 seasons, or whatever. The point being, is that ratings will start to slip, so a few "extreme" things will start happening in the show. Characters will change, some for the worse, but things in the end will be close enough to the last two seasons that people will still be mostly ok. This is where you get the first grumblings.
Season 5 is where the ratings slip really affects things. Stuff gets wildly out of control, and sometimes characters are warped so much that they no longer are recognizable. Most shows die here, unless they're big hits. Then they survive on.
Season 6+ is mostly a different show. Either the dynamic has changed completely, or the characters are no longer who they started out as. The ratings continue to slip, and people get nostalgic for the "good old days' of the show.
EXAMPLE BELOW, MAY CONTAIN SPOILERS FOR SCRUBS
YOU HAVE BEEN WARNED
For example, let's look at Scrubs. The first season introduced JD, Turk, and Elliot as new doctors. It also brought us the staff working at the hospital. They (The new doctors) had to struggle to get used to things, and working their internships. By the end of season 1, they had the hang of things, and became residents.
In seasons 2 and 3, they continued on with their training, fleshing out some characters more and introducing some storylines that weren't "crazy," but actually good (For example, Cox having a baby with his ex-wife. This is actually less weird than it looks, mostly because of who the character of Dr. Cox is.). Relationships expanded, characters grew apart and closer (JD and Elliot)
In Season 4, things started to get a little bit weird. By this time, Turk and Carla got married, the Elliot and JD train had sailed (yes, it sailed), and stagnation threatened the show. So, they threw it for a loop by having Turk and Carla have horrible marital problems, and deciding to make a baby. JD and Elliot get thrown into an "odd-couple" scenario when they're both Chief Resident, and JD gets forced out of his apartment to make room for Turk and Carla
By Season 5, the characters were fully established. There was no more "learning" to be done. this limited Dr. Cox's role significantly, as he could no longer be the "main teacher" of the show. On top of this, JD was hopelessly single, and the storylines got crazier and crazier. At the end of the season, JD found out he impregnated his current girlfriend...after the second date. We even later found out he never actually did the deed, which is even more depressing.
Season 6 is getting even weirder. JD now has an ailment that causes him to faint every time he defecates, and so on and so forth. Many people are tired of the show.
So, what do you all think?