My husband is a volunteer patroller at Jay. Something no one has addressed yet: As a volunteer, he is required to put in 21 days a season. Each resort is different, you'd need to ask Sunday River what their requirements are.
Once you've gotten all your certifications, you also have training throughout the season, have refresher courses in the off-season just before the season starts, and have required training days during the ski season where all the patrollers are gathered to do such things as chairlift evac, toboggan training, etc.
All that said, those who stick with patrolling find it infinitely rewarding and totally worth the commitment. I think it's a good idea to call Sunday River and talk to the Patrol Director, then ask if you might be able to spend some time with the patrollers to see if it's something you'd like to do.