If you are talking about caliper type brakes I have found bmx pads to be more durable than road bike pads, remember everything on the bike will need attention faster with a engine. We are using parts designed for a pedal bike above their designed speed. Do a walk around EVERYTIME you start out, things come loose on a motorized bicycle.
Greg hit it on the head. Also make sure, if you're using rim/caliper style brakes, that the rims are clean and smooth. Rough rim sides, dirt and grit will contribute to brake pad wear. Softer pads will give you good brakes but wear faster. Harder pads require a little more braking pressure but will live longer.
Also buy quality pads. Some of the cheaper department store brands can't stand up to a better grade such as you'll find at a bicycle shop.
If by some chance you have disc brakes, that's a whole different story. Let us know.
Also, if you happen to be using caliper brakes on a painted rim, they'll wear a lot faster. After I sanded the paint off my rims, the brakes last much longer.
i got some kool stops fot 5$, the best 5 bucks i ever spent! Ive stopped way harder on these than my last pair and barely any wear at all. That was a great suggestion Thanks a million