Neighbor had one for 3 yrs and he said it gave up the ghost after this past winter. I've got one for my GH 31 and it is a heavier material but still the Tyvek stuff by ADCO, got it last summer or fall when on sale for around $300. It made it thru the winter ok, a couple small holes were worn thru from the sharp edged rain gutters on the rear, but basically still intact.
If you can get it on sale, it's probably worth it, but full price and I would question the price. Some of the reading I did prior to purchase indicated they would last 2-4 yrs, I'm hoping for 3 and will go from there.
'08 Greyhawk 31SS