I don't think longevity will be a problem.
Galvanized metal should stand up to the elements for years.
I've only had these up for a few weeks now, but I think they will hold up fine.
After setting up a trail camera to check on their success, what I found was these work GREAT at squirrel proofing your feeders.
By looking at the pictures below, I have come to the conclusion that the large end of the funnel needs to be enlarged and I am also going to try the grease and cayenne pepper on the next group.
I'm contemplating changing the cage design as well.
How a full grown coon can get through 1"X2" wire is beyond me.
It does however appear to give him a nice place to sit.