In the tournaments I've played you can only rebuy either if you have no chips or less than you bought in with - depending on tournament. So always rebuy at least once would mean always lose your chips. If you get a solid start you have no reason - and in fact no option to rebuy. This was the case last night, I sat tight for a while (whilst I was cooking dinner) then won some big hands and I was in 2nd place. Maybe i should have gone for the add-on but I hadn't paid for tournament seat I won it.
The whole 10% per tournament would be attractive if I was playing 2k entry tournaments but it isn't that attractive on a £5 entry. Really I want to know how many big cashes 20 x stake per tournament is good is it 1 in 20, 1 in 30, 1 in 50 etc.
Also maybe I'm looking at this the wrong way...
Edited to add on the rebuy thing the 888
99c frenzy is one I used to play and would sometimes rebuy up to 10 times in 5 mins to build a big stack. But the frenzy is about all out aggression -a bit like Russian Roulette