I have a sandblasting gun like this:

https://store.snapon.com/Blast-Syste...t-P666709.aspx

I have a couple of boxes of nozzles for it, that happen to fit
perfectly. They are hardened steel nozzles.

My question is, how many hours of blasting do these nozzles last? I
want to understand how many do I need and maybe I can sell the excess,
as they seem to be selling for $18 each at McMaster-Carr.

i