WIth a 5000 ma lipo, I can easily run a few laps of practice, and 5 minute heat and an 8 minute main all on the same pack. Before I ran Lipo, I was using 3000ma NiMh batts. I would top it off after practice, and after the heat. I would keep my fingers crossed for the main. THe Lipo maintains it punch through all the racing. THe NiMh would start to fall off about half way through the main. It would finish, but would be slightly less than it was when the race started. I can easily get 30 minutes of racing out of the 5000 ma LiPo pack. You mentioned 5 to 6 minutes? What kind of batteries did you have in mind? Or are you learning at this time? Either way, ask ask ask if you dont know. Thats how you learn.
Lipo is the way to go. Last Friday I won the 5 minute B-main and bumped to the 7 minute A-main and practiced a few minutes between each race and had at least half of my battery left after the races. I run a 2c 5400 lipo.
"C" is the capacity in milliampere-hours, in Jerzferno's example, 5000mah, or 5 ampere-hours. The 32C in his pack means that the pack can handle a discharge rate of 32 x 5 amps = 160 amps. Which is more discharge capability than you'll ever need in 1/10 unless you want to use your motor to roast marshmallows. Hope that was clear, I simplified the terms a bit.