I purchased a couple of one hundred dollar chairs. The webbing of couse deteriorated.
Now, a person can GOOGLE for this stuff I had to do it the hard way.
KEVLAR FABRIC
KEVLAR THREAD
Fourteen years later the webbing looks like new. The chairs remain outside. I slapped six coats of marine varnish on the aluminum tubes and bars. After I kick the bucket jesus and brenda will pass them down to the grandkids on and onward.
It wan't cheap but it turns out cheaper in the long run by far. If your chairs are worth it in the first place. Try to avoid BALLISTIC grade Kevlar too thick and too stiff.