dtark:
Also have a 2002 17 but CC. Have replaced the starting battery one time. Boat batteries, in my limited experience of 12 years of boat ownership, take a beating. My choice was a medium-high end starting battery not the deep cycle or dual purpose. Also went convential not sealed. I typically put 70-80 hours per year on this boat with three day trips during the March-October months. This means lots of time in garage storage. Maintenance is critical for longevity.
Depending on source, a $50.00 to $75.00 battery has provided 3-4 years of service. Cranking amps. Reserve capacity? You get what you pay for.