Here's a link to the vest I have. The front side is good for about two hours at highway speed under a mesh jacket. The back, that isn't getting directly blasted by the wind, stays moist much longer. On the bici, I expect the whole thing would last quite a bit longer. Since it's evaporative, when it dries out, all you have to do is soak it in water for a couple of minutes. Running it under water isn't the best way to do it, but it will work if the bathroom sinks are just too gross.