I have some 5103s around here that have aged to a decade or more. Of course we don't have constant gales and thank goodness no salt spray to deal with.
Never had one give me trouble (yet), but since they are way up on a tower at just above tree tops, they are hard to get to. The guys I used to have climb (ham radio guys) have all aged along with me. A young dude who does tree work climbed it like a scared squirrel, but he moved and I haven't been able to get ahold of him lately. The need to work on these things is always on my mind. I look at the antennas and wind and weather stuff on Navy ships and wonder what poor guy gets to go up there to retrieve and fix stuff, especially in heavier weather.
I have had a 5103 get weathered up twice. both times were with heavy wet snow with no wind. And of course the cold afterwards made it freeze solid for a day or two until the sun thawed it enough to drop off.
I can't find it right now but a few years ago I took some close ups of my 'test' 5103 on the back porch with ice hanging off the prop and body. Was sort of neat. The fortunate thing was it was when there was a slight breeze and the prop kept rotating, and the centrifugal force kept spinning the water off, so there were 2 to 3" ice icicles off radially all the way around. I'm sure the imbalance caused errors in wind speed, but my hobby doesn't demand incredibly accurate results, just the fun of doing it. If I find the pix, I'll send them on. By the way, the same thing happened to a Rainwise wind sensor too, with the icicles hanging off it. When the heavy wet snow came down the RainWise was froze up for awhile too. The record looked like it went dead calm. The worse one for freezing up with snow is the Vaisala WXT520, which even with the heater, has a bit of a time getting the frozen precip off the stainless steel dome. I hear the RM Young version of the ultrasonic is much better.