Well, the sound four (five) had to rest after using the level 2 Curse seal, and they probably mastered it properly.
sure, maybe they didn't have three years, and were apprantly complete losers (we should have a disscusion about them, sometime), but they couldn't have been THAT bad. and they probably weren't as damaged in the fight as Sasuke is.

Refernce: chapter 186, way back!