http://www.youtube.com/watch?v=ruPSedayVMU&feature=relatedI'd say like 5 minutes max while completely sober, with no condom, and not having had sex all day.
Of course I could probably go into ADHD mode and start assessing my expenditures that entire month and wondering if they were truly worth it or nut.
also this is for people with DICKS, not penises.