How much EV is enough?

[JP Rocks]

I'm writing this after three spectacular beats in a row in the stars $11 MTT (no rebuys). I managed to call all in with the best hand each time against someone who had me covered, only to find myself sent to the virtual rail. (TT v AA on a Txx flop, A, x; AA v KTo preflop, Qxx, A, J; KK v AKo preflop, xxx, x, A). Each of these times, I had a slightly above average stack, and had played conservatively thus far.

My question is this: How big of an advatage do you guys need to call for all your chips in the first hour of a low buy in tourney like this? Usually, I need to decide that I am at least ~70% favorite to call for all my chips, and as such I was pretty happy with how each of those hands went (without being results orientated). Should I be more cautious about getting all in (preflop especially) in the early stages of a low limit tourney like this against opponents who have me covered, or is this just a bad beat post?