How many times should you rebuy in Empire/Party tourneys

[z32fanatic]

With the empire/party rebuy tourney allowing you to rebuy as many times as you want, how many times should you rebuy? I have been doing it 3 times total and adding on, giving me at least 5500 after the break. The problem I find is that although I will money more often, if I don't make the final table, I will lose money on the tournament. Does anyone have any thoughts on at what point rebuying becomes -EV? Any thoughts or advice would be appreciated. Thanks.