Our Jayco 23ft Class C motorhome had the spare attached to a carrier which attached to the rear bumper. Was still very snug after 40K miles. We kept it covered with one of those plastic spare tire covers.
Our current Aspect 26A has the spare mounted on the back with a very nice metal cover so no uv rays get to it. Have about 20K miles on this one. I check the tire pressure periodically.
Be sure to mount it inside out.....turned around so the flat side is against the carrier. You may need an extension to reach the nut or just use the lug wrench to tighten it down.
I feel much more secure with a spare tire on the back. I also got a torque wench so I can properly torque the nuts. Then I practiced taking the rear tire off and putting it on just to be sure that I could.
Good to have a spare even if you have road side service. That way you don't have to pay big bucks for a replacement in the middle of no where.