Okay, the weather has nothing to do with this. Landing in DSM for a problem could have been for specific aircraft with a common problem. Tell me this: how many windshield heaters woud you keep around for each of UA's 8 different aircraft types (727, 737, 747, 757, 767, 777, DC-10, A320family--not to mention the innumerable series types) at DSM? Not many as that type of accident doesn't happen often!
life is a journey, travel it well.