I feel that. Mine lives under a cover as well and gets sun all day, every day. I'm in So Cal which is pretty hot and dry but not as much as Coachella Valley. I've been through a ton of covers for this and the various boats I've had.
So what I've learned over the years on covers is something like these options
- Go Cheap - Get a cheap cover and just plan on replacing it often. That said, I've had cheap covers that started falling apart after 6 months but usually I'm aiming at a year if I'm lucky
- Go Mid - Get a name brand, semi custom cover with a warranty. It almost certainly won't last the duration of the warranty, but you at least have the possibility to get a discount on a replacement when it does fail. This is what I've been doing the last few rounds
- Go High - Get a better cover made from something like Sunbrella fabric that will last several years at least. Expensive and probably more expensive than replacing the cheaper ones more often. I've gotten around 4-5 years out of this route.
The other thing is take care of the cover. Try and keep it cleanish and I've even applied some UV protectant on my covers every now and again. Can also make it easier to keep them clean.