If you are talking 2K-3K miles per year driving during the next 10 yrs., I would stick with gas. If you are going to retire soon (next couple of years?), then maybe I would consider a diesel.
In my opinion, a diesel does not like to sit, they like to run! We put about 10,000 a year on ours as we use it once a month. We have already put 6,000 miles on our new one since November (had 3,100 at delivey so we are showing almost 10,000 miles).
Another thing to keep in mind is an 8 yr. old coach is going to start needing things just from age whether it's a gas or diesel. Tires for sure and some of the windows (if double paned) may have started to fog. Check everything!
Good luck,
MM.