My limited experience has been that some kits are a bit more prone to bombs than others. I'ver had three bombs in total and all were with the ESB bavarian lager lit, for some reason they have had WAY more carbonation to them than any other kit I've brewed. The second batch of this stuff I did I had two bottles go ballistic on me, luckily I'd bottled into screwtop stubbies so was able to gas of the entire batch a little, they were bottled in october and have since survived the heat of summer without mishap, and have been drinking fine. I suspect that fermentation was incomplete when I bottled these, they tend to have rather excessive sediment in them, obviously the 11 days I gave then wasn't enough. What scared me more was when a bottle of an earlier batch that seemed to be fine went a mont hor so later after I had moved them, I can only suspect that moving the bottles got the sediment stirred up and got the yeast working again and send one of them off.