I recently traded in my 1974 JD 2030. After 38 years, it looked almost new. It had been barn kept before I got it in 2001, and I built a shed for it next to my workshop. Sure some rain and snow might blow in on it, but not too much. My neighbor has a tractor almost the same vintage. It still runs well, but has been kept outside most of the time... And shows it. It is so rusty that you don't see the JD green, and bolts and levers are rusty and had to repair.
My new CUT stays in the shed when not in use. I expect to leave it to my kids, and want to leave it looking good.