I'm not sure if we are playing in the the same place or not, however I have a strategy that I use on almost all of my R/A tournaments. It could be WAY wrong...
I wait till the break after the last level of rebuys right before add on and do both at the same time. This prevents me from rebuying to much and lets me avoid the early shovers playing like donks. Yes you can make a case that those are chips you are missing out on, this is just my preference.
Some may thing this puts your stack at a disadvantage. While you won't go to break the chip leader I have found that I am almost always right on par with average stack. I also have between 20 and 30 big blinds to play with which keeps me out of the shove/fold spot that a lot of late reg tournaments put you in.
This is not the case for every site just the one I play on the most so results may vary. The point is you have to look at all the variables in the structure and what rebuying and/or adding on will actually do (if anything) to your chances of winning the tournament.