[Kurn, son of Mogh]

I recall FossilMan saying that if you're not willing to take every rebuy and add-on to which you're entitled, don't play rebuy events.

I also recall some other pros saying that they assume they'll make an average of 7 rebuys evey time they enter a rebuy event. I think that's a good rule of thumb. If you're not willing to consider anything under 7 buy-ins as getting in cheaply - don't play.