I have a 22 inch Blackstone, when we moved to our current location, I didn't use it for about 5 or 6 months and it got some rust on the griddle surface, but I took my drill and a wire brush adapter to it and re-seasoned and I haven't seen any rust since. I do have a soft cover for it and I store in my man shed. I use it every two to three weeks. I've had it for about 6 years now.
I'm about to replace it with the newer 36" 4 burner culinary omnivore. It's $100 more than the other 36", but has new welds on the bottom of the griddle along with the wind guards. I live on the coast and most days are breezy and I hope this one will work well.