My Maytag racks lasted about six years before they started rusting, and after eight years I replaced them. I don't think that I'm unduly hard on the dishwasher.
At only 3.5 years you might want to replace the racks if you can get them for under $200 at the source I got mine (pointed out in an earlier post). I don't recall any other dishwashers that I've had having the racks rust as fast as the ones on the Maytag, and they've been replaced for other reasons.