When I'm in the studio w/ people making on the spot tracks I take about an hour to get the meat going and another to finesse it out...I track it out and bring it to protools to mix with the vocals...
At home I'm more critical, I don't like spending more than 2 hours on a beat, I feel like part of the greatness is hearing the potential in every sound rather than spending all day making one perfect...I like this shit to go...I feel like if you are great then great music comes out...I have a method of creation that is kind of mixing while you go as well...Learning to spend less time tweaking and more time creating is what I strive for now.