I'm using a Tonic Z10 3700kv with a custom 14 tooth pinion, driven by a Castle Creations Phoenix 35 BL ESC & Mega Power 20c 1350mah lipo's. Run time is about 12 minutes in Normal Mode & 8 in Idle-up. Pitch curves are MAXED OUT at +11 & -11, I run ST1 mode at 70% throttle (this is where I mostly play), & ST2 at 90% (runs like a V12 in a SMART CAR)!
The motor never gets hotter than 125 degrees & the lipo's end up around 105 to 108 degrees after a run. If your motor gets HOT after a 8 to 10 minute run, then I would gear-down on the motor pinion. If it's a 15 tooth, try a 14 or 13 tooth (if you can get them to fit your motor shaft). I ended up taking a variety of stock pinions (0.4 pitch), and machining them to a size that would fit the Tonic BL motor with a slight press-fit.
If your Lipo's are swelling after each run &/or are hotter than 120 degrees, than the current draw from the motor is too high. I had this problem with the 15c MP lipo's I had with the stock motor, by upgrading to the MP 20c lipo's it hasn't been an issue anymore.

Shadow