We are having lots of problems with wheel bearings rusting and wearing out on our Wipline 2100 Amphib floats. We grease the wheels regularly but the bearings are rusting after only about a month of use. The airplane is used for training so we do lots of water takeoffs and landings but very few runway landings. Has anyone else encountered this problem? Is there any type of sealed bearing system similar to what is used on boat trailers? Any ideas, suggestions or recommendations would be much appreciated.