It's proportional. The less it is exposed to rain and UV, the less damage and degradation will happen.
And the less sun, and wind the cover is exposed to (and the tighter it fits and care taken when installing) the longer a cover will last.
And the more care taken with maintaining the camper, the longer and better it will last.
And if you put it in a bubble it will look like new 100 years from now and if you park it in Death Valley, it will look 100 years old 3 years from now.
Cover costs, what, $300? Avg lifespan 3-5 years? Say 3.
Is it worth $100/year to protect it from the elements?
Millions of people don't garage or maintain their cars either. Does that mean its bad or not worth it to do that? Nope, just means millions don't care or cant' afford to garage their cars....
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5โ turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold