We have an 8 foot Arctic Summit that is 3 years and 10 months old. For the past year the cover has been very heavy and has gradually gotten to the point where I cannot lift it on my own. The cover is a castcore cedar, that came with the spa when it was brand new in October 2009. The hot tub has had very little use...less than once a week, no big parties, no abuse etc. I am amazed that the cover already needs replacing. There are no visible holes anywhere and no damage. Anybody got any ideas on why the cover already needs replacing? I really need to know what the best cover to buy would be as I don't want to have to replace it every 3 years. Which ones last the longest and at the same time provide the best insulation? Thanks!