I have a Liberty Z 48" that has proven to be trouble free at least to this point. But having it for three years now with only 98 hours of use, I guess that is not uncommon. I know of the 6 grease points that I attend to at the start of each season, but noticed there aren't any zerks on the spindles, which I believe means the bearings are sealed. Is there reason to feel that I need not worry about the spindles, or perhaps is there something I can do to prolong the life of them?