Let's take a look at the 2011-12 season (the ninth overall) of Two and a Half Men on CBS.
Rating the Ratings: How do we evaluate a season that started off with higher ratings than we will probably ever see again for a regular scripted series and ended down year-to-year in the last few eligible comparisons? Depends on your perspective. If you're looking at this season from that premiere night when Ashton Kutcher's debut scored a 10.7, it sure doesn't look good that the show shed nearly two thirds of that demo audience by season's end. If you're looking at it from the moment Charlie Sheen was kicked off of Men, though, it's a hugely different picture. If I'd told you at that point that they'd renew the show, replace Sheen, and be up 11% next season, it'd have looked like one of the all-time TV successes. Personally, I think both sides have a point, but I think the second perspective is the big takeaway and the first one more of a subplot. Even if you assume the -5% or so of the last few weeks is where the show "truly" ended up, that's still a very good result for a ninth-year show replacing its lead. Yes, they had to pay Kutcher a lot of money, but it was not any kind of given that the show would hold up at all. Just ask post-Steve Carell The Office about that. Grade: A-.
Here's the now updated War of 18-49 post for Two and a Half Men.