In Florida, I had cover on my little 26 Commodore for 7 or more years and never had any problem with them... actually didn't even know they should probably be serviced regularly.
In the Caribbean, on my 36 after 3 years I had one winch that would stick and not lock immediately a couple of times and had a guy show me how to clean it. Only then did I find out I should service them about every year!
I don't see anyone in the Caribbean with covers, well actually maybe twice as I recall but only one seemed to have a full complement. That may be the reason, they can be so easily lost and just something else you have to store and retrieve between sails. I think if I were someplace where lots of dirt or possibly ice could accumulate I would consider them. Until I see some $$$ value to having them in the Caribbean I'll probably pass.
I prefer a sailboat to a motorboat, and it is my belief that boat sailing is a finer, more difficult, and sturdier art than running a motor.... Jack London