Our pool season was cut short last year by an unbelievably rainy September and October (lots of lightening and the types of storms that meant flooding all over). We are surrounded by trees and put our leaf cover on pretty much for the duration. Our SWCG generator and pump ran on schedule except for the occasional power outage. I’m not sure our temperature dropped below 60 till November. We drew water from the skimmer or loosened a corner of the net if we expected to be adding chemicals. We never added chemicals to the skimmer itself.
We actually don’t close our pool at all in winter because we might get the occasional freeze, but it’s only a matter of hours usually. We use the mesh cover all fall, winter, and early spring until our live oaks are done dropping leaves and catkins. Our mesh isn’t particularly thick, and we never noticed a buildup of CCs from having it covered. I’m sure different brands are different thicknesses.
Our net also does not usually touch our water (torrential rains excepted) because it’s put up over a safety net. We’ve not seen algae grow on it, but our pool remains open, properly circulating and chlorinated underneath. It is a big help to keep from having to empty the skimmers constantly in the fall.