I believe it was John Water’s who said that no comedy should ever be more than 90 minutes long — a good rule of thumb. After all, most comedy concepts strain credibility from the very beginning and as writers/directors stretch them out the comedy thins out, pulling the laughs farther and farther apart. This is why a movie like Airplane! is considered a classic and This Is The End will never be anything more than pleasantly amusing. With Airplane!, the laughs fly at a mile-a-minute pace. With This Is The End, not so much.
In other words: too long.