If you've got the Addco Tyvek cover, they last 2-3 years in the hot sun, max. I've had two of them. Your 3 year warranty will allow you ONE free replacement and you can deal direct with Addco on this, as we did. All you have to do is cut out the printed section on the front with the information and send it in to them. They sent us a new cover shortly thereafter. The new one lasted a little over 2 years in the hot So Cal sun. No more Tyvek for me. I think I will try a Goldline polyester cover the next time around. Costs more, but comes with a full 5 year warranty and is not Tyvek junk.
Having said all that, I kind of have a Love-Hate relationship with RV covers. They keep the rig nice and clean but can be a real PITA to put on and take off.
Did I mention Tyvek is JUNK?