Charlie already made this point, but I thought I'd use the PitchFX from BrooksBaseball.net to drive the point home: Ian Snell's start last night is a great illustration of why pitchers generally aren't allowed to throw more than 120 pitches in a start. Check out the velocity plots from his April 29th start against the Brewers and compare them to his start from last night:
Besides the difference in pitch speed (the average of his fastballs according to Pitch FX dropped almost a full 1 mph last night), it seems to me that his velocity was much more inconsistent last night, and maybe only 10 of his last 40 pitches even topped 90 mph. This is an obvious statement, especially if you've ever pitched before, but you always feel better on the mound than you do the next day. Maybe Snell felt great after 110 pitches last week, but it seems pretty clear that pushing him forward in that game had a negative effect on him yesterday.