Time for new batterys

[ridinbikes247]

alright, hers my set up
hot bodies 1/8 truggy with 15/50 gear
2-3300 Mah NiMh battery packs in series
8 XL feigao motor
Mamba Max ESC runs 120 degrees F
motor and batterys run 70 F
i got 6 minutes run time with that set up
I'm aiming for 15-20 minutes run time, is there a way to do it with NiMh..maybe a 5000 Mah venom
If not what type of Lipo should i be on the look out for ? should i run 1 lipo or two ?..i want to stay with Nimh but if i cant get 15-20 minutes out of them i guess ill have to go lipo