There is no such of thing. A good cover that will last awhile is something like a Calmark but expect to pay $500+. Its either that or keep buying the less expensive ones and figure on replacing every few years. Thats why I invested in a metal carport. One season with messing with a cover was enough for me.
First time I put mine on it got caught on the tv antenna and I ripped a hole in it before I relaized what happened. (And yes the antenna was down). Its been duck taped and I'll be able to finish out this winter. I figure its cheaper just to buy a new cover than to pay for months of covered storage since my tract home has no room for permanent covered storage.
I always used those heavy duty brown and silver 2 sided tarps from Lowe's. Cost was cheap and they lasted a good long while.
If I were to have bought a real cover, I would have had one made out of that heavy duty blue canvas they use to make boat covers. Those seem to last for a few years. I'm sure it wouldn't have been cheap.
I've had an Adco Tyvek for several seasons. It has one tear, which was my fault (pulled straps too tight), but otherwise in good shape. I got the next size up so there is some extra room, which I just fold up in the back.