Yup. Some games might be problematic (IIRC Dungeon Defenders from 2012's HIB7 is a known one) and might give duplicates but these are pretty rare and support should be able to help in those cases.
I had an issue with one game once: keys were out of stock.
Thanks. I've got about 20-30 keys for old indie games. Hollow Knight, Inside, Owlboy, Mark of the Ninja ... that kind of stuff that everybody has, but they're good games. Debating bothering to redeem them all because everybody has them, but I'd hate to waste them! I wanted to make sure that if I generated the keys, somebody could actually add it.