I keep a plastic reel around for 35mm that just won't cooperate. I like knowing my film is on that stainless Hughes, but honestly, I never see a lick of difference in the final images between plastic and steel. Plastic's a little harder to dry if you're doing several rolls in a row, but either way I'm grabbing a hair dryer and it just takes a minute.
Plastic's the only game in town if you do a lot of testing and run partial rolls. I find the clips on the steel reels waste too many frames, and it's so simple to get a few inches onto plastic - especially with 120 film testing.
All of my reels are 15- 20 years old and none of them show any signs of aging, plastic or stainless. But keep in mind, if you try a plastic reel, they won't fit in your steel-reel tank, they're a little larger.