use regens sparingly, and strategically. try to make the other guy run outa regens first, then you have plenty of time to finish them off. I see them as similar to having a wild-card or a joker. If you use up your 'mulligans' too early, then you will be toast. but if you don't use them at all, then you might find yourself respawning earlier than you had anticipated
I use nanobots when my hull takes a serious pounding and gets down to about 50%, or if I've had minor damage for quite some time. Also if my hull is exposed and I hear the missile warning message I'll heal up my hull and sheild. I usually only fight dirty against missile toating Ravens Claws (every single Ravens Claw I see had duel missiles) or if I'm just plain bored and want to kill them fast.
Also if I'm against a bomber and my shield is down, or if I'm in a light fighter chasing mine spammers I'll try keep my shield up as long as possible.
Basicly the only place you wouldn't use nb/sb would be conneticuit.