I agree. The problem with spacing is, the injury could wipe out your opportunity to get everything out of him that you can.
Let's say you have Tomo Ohka, and figure you can get about 13 starts out of him. You start him about every other series, so that after 120 games, he's made 8 starts. You should be able to get 5 more starts from him, but in his 8th start, he gets injured and misses 60 games.

This is exasperated if you're hoping to make the playoffs. He'll be limited in how often he can pitch in the playoffs, but unless he gets hurt early, you could wind up losing him for ALL of the playoffs.