[starscream]

Hmm, 16.75 : 1 sounds a little high so I wouldn't be surprised if the the run time is shorter.
The stock e-maxx gear ratio's are:
1st gear: 28.9:1
2nd gear: 17.9:1

If/When you get a brushless system, I would recommend running the truck ~20:1 gear ratio, so probably a 15t or 16t pinion.
Nowadays, I always error on the side of caution (rather start with too low of gearing than high). You can always gear up if its too slow.