With the advent of Ni-MH batteries unless you are running very silly motors runs times are now much longer. Even running a 15x2 motor I can get 15 mins out of my Blitzer Beetle and thats a real old school technology buggy/truck, although fully ball raced its hardly the best chassis ever created but it seriously fun and only cost

You can now get 5000mAh Ni-MH packs although they are still expensive.

Only problem I find that you tend to forget with the longer run times just how hot things can get..lol.