My 10'x16' fastrack layout is from the mid 2000's. The only fastrack I've had rust was accidentally forgotten for a couple of weeks on a deck railing outside after being used for a sale ad.
I've even had a portion of my layout get wet a couple of years ago ( don't ask). Pulled up the track, dried it off, ran a fan and dehumidifier for a few days and the track went back down good as new. I even had a remote switch get wet, after drying out, works fine to this day.
Having said all that, my layout is in a "newer" basement, drylock on the walls, as well as vapor barrier insulation, and epoxy on the floor. Its fully heated and airconditioned ,even so, a dehumidifier is still used most warmer months when the humidity is greater than 50%.
Not only is this good for my trains, its good for the T.V., furniture computer, etc. etc. even myself.
While I cannot say fastrack is or isn't inferior to old tubular track, an attic environment is as extreme as it gets.
I understand folks here come from all financial levels and are limited as to what they can do. However I've seen posts where layouts are in basements that regularly have standing water on the floor and the members don"t even have a dehumidifier, I just cringe.