Take your seat off when you wash your bike, especially if you have an aftermarket seat cover. This is a cheap and easy way to extend the life of your seat foam. As you can see in the photos, water can get into your seat foam from washing, as well as from wet and muddy riding conditions. You can see the ribbed pattern of the seat cover has transferred onto the foam at each of the seams. Unless it says so, most aftermarket seat covers are not water resistant, while most OEM seat covers are. Over time, the foam begins to crumble and just sort of fall apart from getting wet. It can also get waterlogged and start to weigh a lot. The seat in the photos is only a year old, and it was removed during the majority of bike-washing sessions; the cover was removed to inspect the foam. But the bike is a GNCC racebike and it saw a lot of muddy, sloppy, wet conditions, so some degradation is unavoidable.