I started with a used 36' DP because of posts on here that 36' was the max for NP, SP, USFS, ....... did not take long to learn that was not true so traded for a 40' and 12 years ago 42' plus I built my MH bay long enough for 45'. In Yellowstone it's easy to make a 42' become a 40' for their max length sites:W... would be harder to make a 45' into a 40'.
In the East and in CA it's a bigger problem finding Public CG sites big enough (not impossible) and in the West it's much easier. My 42' has a slightly better turning radius than a non tag 40' as the drive axle wheelbase is shorter... not so for 45'. It is amazing how much better a tag axle coach handles even though my 40' was a RR8R Beaver. There is a lot of truth that once you have a tag, you will not go back plus having 9000+ lbs of CCC makes it too easy to keep too much stuff. If I had to replace this MH I'd probably go with a 44 or 45'.