I think I will throw you a curve ball...forgive me I'm off base but hear me out. I shot with a glove for well over 50 years. I went off to a buddy's house to do some stump shooting about 5 years ago and forgot my glove. Then I was shooting 60+ #s so I needed something and was forced to try one of Todd's tabs. I have never shot a glove again and now I have about a half dozen tabs, all cordovan, and have had to use only one (except for the one I lost) during those 5 years or so.
But, I can answer your question. The damascus gloves, for me, were very short lived. They are very thin and soft. And in a way you have answered your own question. Basically when the day comes and you have to ask yourself the question, then it is time to change gloves....IMO.