Agree with mysterio. I do have extract recipes that call for boiling the bittering hops for 45 minutes, than adding malt extract (local HBS). However, most HBS (Austin HBS, Midwest HBS) and books recommend boiling the hops with the extract. However, having said that, both methods seem to produce a good beer. The process is somewhat forgiving. The flavor and aroma hops come at the end of the boil. And let's not forget dry hopping!!