Our boat has about 410 hours on it. Had it in recently for a leak (another story) but had the packing adjusted at the same time. Mechanic said it looked like it had never been adjusted. He tweaked a little bit and said we had a LOT of room to adjust more. I'm not sure if it sitting is bad or not. Like you said now is the time to replace if needed. Access to the packing in a V drive is a nightmare.
1998 MariStar 200 VRS, LT1, PowerSlot