How long can a 4s 4100 lipo last?

[Finnster]

No way it will do 15mins unless you are drving quite slow. 10mins may be doable, but will be close. FWIW, at the few RCM bash's I've been to, the guys w/ 4S 5000 packs were doing just shy of 15mins on their truggies. Really I would count on 10-11 mins. YMMV depending on driving style. Really you want a bigger pack to make 10, and ~6000 mah to be sure to make 15.