production - What happens to actor salaries around seasons 6-7 of a show?

If I remember correctly, the standard contract for headlining TV actors is for seven years; with some options of renegotiation during, options for dropping out, being written out, allowance to take on other roles, etc.

After the contract is up, and the TV show is still popular/makes money, the actors pretty much make the show what it is (in the eyes of the majority of the public, at least), so they have an upper hand in asking for much bigger salaries. It also happens that after those 7 years, the contracts are renegotiated every year or every two years, and their salaries go through the roof (recent example: Big Bang Theory main actors).

During the first 7 years though, and you might have noticed that on many shows, actors get the "executive producer" credits, even if they are not directly or even indirectly involved in the decision making or creative process of making the show. This is one of the ways to bump their salary or provide honorary title, which gives them more bargaining clout in the long run.