Having had a chance to play a few more MTTs and following the advice in
this thread regarding rebuys, I'm gonna have to modify what I said earlier and confirm Noone, Danzi, and Razz to be partially-correct.
You play MTTs to win, not to just "cash-in". In the past week I've rebought and adding on multiple times in games, playing very aggressively, in order to ensure a good stack before freezing out begins and eliminations are final.
Similar to my previous argument however, I would advise that there are certain times to account for, that you modify your betting style.
Prior to Prize Pool, and Right after Prize Pool.
PPP - At this point a lot of the lower stacks (yours included) start tightening up and praying they make it to cashing in, at least to make the past 3-4 hours profitable. Larger stacks will attempt to raise on weaker hands in order to bluff lower stacks out of their blinds.
You might find it easier to win against larger stacks in this situation, and would be the time to start building your own stack. If it's you versus and smaller stack, and no large stacks are involved, you can try bluffing, as it will work better on someone worried about going out right before cashing in.
RPP - Once cash is guaranteed to everyone remaining, people start to loosen up and begin to play, bet, and risk more. You might find it beneficial to either play a strong hand against these people in order to build your stack, or to let others eliminate them in order to climb the prize ranks.
I suspect you will not have an easy time bluffing your way through at this time period, so make sure your hand is good.
As for your original question, which is about being short stacked and blind vulnerable at any given time of play. Just do it. Remember that even AA can lose, and nursing a crippled stack that doesn't have the magnitude to recover without multiple back-to-back wins is going to usually sputter and die.
You need to maintain a stack large enough to bring you to the safe zone after 1-2 big hands. When your stack is so small that you need 3-5 wins to recover, you usually already be past the point of no return.