I guess it depends on the games you play and your style. If you play a very LAG game at the NL100-NL400, especially HU or shorthanded then 2 buyins is nothing; 5 or 6 seems more realistic. If you face a bad opponent who gets lucky a few times you don't want to leave because of your overly tight rule.
On the other hand, I don't know when and to what extent dropping 3 buyins bothers you. If it does, then it's probably better to draw the line one buyin before you get frustrated.
Bookmarks