These little geared motors are designed to be 250w motors, pushing them harder is possible but the more you push the more you have to be carefull not to destroy them ( first thing to go are the nylon gears .. ) 36v 20~25 amps is still reasonable, but is about the limit before things start to be sensitive. some guys are running 48, 60 and + volts on them but that's way over the limit for these mini's.
Ride your normal route and pull over to check motor temps with your hand once in a while, if it remains cool you are not pushing it.. if it's warm you are ok.. if it's hot need to lighten the load or ease off on the throttle lol..