IMO the life expectancy of a treestand depends on how well you take care of it. Many hunters leave their stands in the woods year round and exposed to the elements. I take mine down after the season each year and perform any maintenance that needs done. I think leaving them out would reduce the life of the stand. In your case, since it is a climber, I assume you pack it in and out and don't leave it in the woods. I would say as long as you feel safe it it, keep using it. Happy Hunting!
My pursuit of a buck of a lifetime is much like the Chicago Cubs pursuit of a World Series...the season ends with a "wait til next year"