I've never had the pain switch sides on me, but I have had CH for about ten years now and tend to have attacks from the spring to fall equinox, plus or minus a few weeks. I find myself looking forward to Halloween even more now, because that's when it stops for me in most years. But I have had from spring equinox to the winter solstice as well where I only have a couple of months of being pain free until the next spring equinox. It is weird how those four specific times of year seem to have an effect on most people with cluster headaches.