60 minutes is standard for a bittering addition. Pellets are no different from leaf hops in this regard (utilization can be a bit higher, though). Shorter boil times means less bitterness, more flavor.
I'd suggest perusing www.howtobrew.com (the first edition of Palmer's excellent book, available free online). Lots of this kind of information is available there. Read it, re-read it, buy the paperback, put it in the john, read it a third time.