Lipo with a brushed set up

i would e mail the company that makes the esc your using to see if you can. as for run times you will get a longer run time but it also depend on how your driving style is. i can get 20 minute run times with my stock 18b.

Danny's on the right track. You'll need to see what input voltage your ESC can handle. I'd assume you're thinking of running a 2s lipo which is 7.4v. I would suspect that the ESC can handle it just fine. However, you'll need to consider the physical space that you have to mount the batteries in. If you're looking for longer runtimes, the key is the mAh rating of the pack. That's no different if you're using lipo or NiMH. Bigger mAh rating=longer runtime. Bigger mAh rating also means bigger physical battery size so you'll have to consider that.