People charge them to the max to get the highest voltage they can. But if you want them to last longer undercharge them a little.
And NEVER re-peak, if they have been charged a while and you feel the need to pep them up a bit, put 200 seconds of charge into them and cut the charge manually. They don't tend to re-peak very well, and that
usually when they go bang if they are going to.
All the above is my own personnal opinion, I would rather people do not come back and flame me for it like usually happens on the 'When IB's go bad' threads........
G