I would think you'll be OK as long as the motor doesn't get too hot. You can measure this qualitatively on a geared motor by putting your finger on the motor; as long as you can hold it there for 10 seconds, the "experts" say you're OK, that is the internal temperature of the motor is below 180 degrees or so (possibly your system has a temp sensor that will shut it off automatically). However, you'll probably be able to sense if the motor is lugging.