Breaking the 30 minute barrier on DSLR cameras

I currently use a conventional camcorder to record plays at our local theater. It is not HD and am considering a dslr to improve the quality. The play length usually runs from 90 to 120 minutes. Is there a way to get around the time constraint of 30 minutes? I have room to have a laptop computer next to the camera if that would solve the problem.

I know a dedicated HD camcorder would solve the problem but I would also use the camera for still photography.