Made A Mistake

I would surely continue with the rig already owned and paid for, even if the Tioga was well cared for at a lower price. The mileage on your old rig is not concerning. Since you like it, just keep enjoying it. When you get to 125,000 miles driven, then you might start contemplating how much longer until ready to make a switch. You could get over 200,000 miles without major issues, but you'll have to be well disciplined with maintenance.