IMO,
If you lose 1/3 your original stack, you need to stop and reevaluate the gameplan. Take, for instance, a Stars MTT, which starts you off at T$1500. If I run into a few bad hands, or whatever the case may be, and I find myself below T$1000, I usually stop limping with my multiway hands and wait for hands that I can just play aggressively. At this point, you really can't afford to keep limping because now (esp. as the blinds increase) it's hurting you more and more.
__________________
|