Well, I use a strategy with these types of tourneys, it relates to BRM, stack size and reason for felting. It's something that I came up with after a lot of reading and my experience with MTTs.
Firstly I always budget on a max of 2 rebuys and 1 addon (This is in line with my brm). It also makes sure that I don't put more cash into the tourney than placing in the money will get me back.
Secondly, I will only rebuy if felted when the number of chips I get for a rebuy is over 50% of the average stack size in the tourney (This uses stack size to determine whether or not I rebuy. e.g: if the average stack size is 10k and a rebuy gets me 3k, I won't rebuy) This ensures that I am not just feeding the chip leaders.
Lastly, I will only rebuy if, when the money went in, I had the best hand. This forces me to make good descisions in the early stages of the tourney before the end of the rebuy period. This is more geared towards my MTT strategy, but I have found it the most useful of the 3, in terms of number of tourneys I enter vs the number of times I place.
In terms of Bankroll, I will not buy into a tourney unless I have 100x the buyin amount. So for a 1k Bankroll, no more than $10 buy in.
By no means the only way, just what works for me.