Used Diesel Motorhomes

I drive my motorhome in the range that you indicated! That's why I didn't buy a D.P. and stayed with gas. If you still want to get a used D.P. I suggest you browse www.DemartiniRV.com

A 5-8 year old coach will be 15-18 years old by the time you plan to get rid of it. At the high end of your expected usage, you will add another 30,000 miles to the existing mileage on whatever coach you buy.
You will not wear out the engine, whether it is a gas or diesel power plant. Your friend racks up a lot of miles, so for him a diesel MIGHT be the best choice. Many of us have had both diesel and gas coaches. I have never heard of anyone on this forum actually wearing an engine out, whether it is gas or diesel. There have been instances of both engines having catastrophic(very expensive) failures but it was due to some other outside cause rather than the engine being worn out from just racking up the miles.
Based on your description of the type of trips you plan to take, I would recommend a gas coach and save the extra cash to buy other items. With short trips the larger fuel tank is not very important. With your schedule, you will be spending more time parked at your destination than driving down the highway.
I would concentrate more on a floor plan that you both like and put the type of engine way way down on my list of things that have any importance in your enjoyment of the RV lifstyle. .

We started with a gas class C and the experience is similar. Class A gas have: Spring suspension, shorter fuel range (80 gallon fuel tank vs 100 - 150 on a diesel) , and depending on the manufacturer can be very loud. It depends on how long you travel away from hookups. There is no question that diesel engines last longer.

Class A gas pros
Lots of floor plans available
Lots of inventory
Lower initial cost
May have disc brakes

Class A gas cons
Poor towing capacity typically no more than 5,000#
Very loud inside depending on floor and doghouse insulation
Longer rear overhang (be careful getting fuel)
More frequent service than diesel
Service centers are typically only at Ford Truck and motorhome shops that have limited hours of operation
Harsher ride with spring suspension
Coach systems are not as integrated
May need suspension and or steering upgrades depending on the manufacturer.
Lower fuel economy less than 10 MPG is common 5 - 8 is very common in older units
Shorter range typically 300 - 500 miles
Smaller tanks (80 gallon fuel is common, 30 - 80 gallon fresh water, 40 or less gallon grey and black, 10 - 30 gallons of propane)

Class A diesel pusher benefits
Quiet ride with no engine noise
Soft stable ride due to full air suspension
Typically have well integrated coach systems
Automatic Generator start (depends on year)
Panoramic front view
Very quiet diesel generator
Excellent turning radius for the size of the coach (a 33’ DP will usually have a 208” wheelbase and a 55 degree wheel cut and can turn around in a standard street)
Fantastic, fuel capacity (Typically starts at 90 Gallons and goes up to 200 gallons of diesel depending on chassis) gives a realistic range of 1,000 miles on flat ground.
Excellent water tank capacity – typically starting at 90 gallons and ending up at about 150 gallons
Well integrated coach systems
More living space for a given coach size
Engine exhaust braking system (Pac Brake, variable vane turbo or other great system)
Usually any truck diesel shop can work on them and many are open 24x7
Chassis and drivetrain lasts a very long time
Long service intervals
Better manufacturer support
Have tow ratings starting at 5,000# to 50,000#, depending on coach some very inexpensive units have tow ratings of 10,000#
Large battery banks
Large residential refrigerator (less common on older units)
Heated wet bay
Neatly run wiring
Weight ratings starting at about 26,000 GVWR up to 55,000# GVWR with a tag axle with GCWR ratings of 30,000 up to 80,000.
Better fuel economy for similar sized units

Class A diesel pusher cons
Limited inventory
Higher initial cost
Higher cost per hour for service
Typically more complex due to better integrated systems
Limited floor plans (I only found a few floor plans that had bunk beds and a 10,000# tow rating)

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.