That's good in theory but rarely works in practice. You might go 5-6 days of getting 5+ innings out of your starters. You won't give a single reliever three innings in any of those appearances and May rusts on the bench. The reason you don't give one reliever three innings in that situation is because the game is usually close at that point and you want to use matchups to notch another win. If your starter goes 5+ and the game isn't close, you're probably kicking the other team's ass so it doesn't matter. On the other hand, you might get a couple of three inning starts in a 2-3 day span. You can't use the same guy for three innings that close together, either. And if your starter goes three innings, you're probably getting your ass kicked so, once again, it doesn't matter. The reality is that long men don't get regular work. There's a reason why long men are the back of the bullpen and very rarely a good pitcher. You use them when you need innings en masse and don't want to waste all those days off on a pitcher who can actually get hitters out on a regular basis.