Tactics... Fast or Slow?

I'm working my way through the chess mentor (which is freaking awesome) but I'm trying to play a bunch of exercises in the tactic trainer. I go slowly through the chess mentor, reviewing each leasson after I complete one. I'm learning a lot.

My question is, should I be doing the same thing with the tactics trainer or should I just try to play a bazillion (technical term) until I get good?  

My thought is make sure you understand the tactic otherwise 500 won't help anymore than 50.

Awesome. Makes good sense to me. Thank you Nswwsn and Estragon! 

Yes, the slower you play the more you learn.

@OP: nswwsn's advice is excellent. When I do tactics in TT, I disregard the timer and make sure that I find the best move. I always remember the advice, "Don't move until you see it." If I lose points for passing a problem, I don't fret. Rating points will come later, but first: patience.