Myself, unless required to do so would not hang on to them at all. There is always some prig that'll tool along wishing to make a spectacle of himself and second guess you.
The other issue is, a plant I worked at some years ago maintained at any given time more than 100 welders. We also had periods of hiring and laying off of course. And we did anything from Csteel to HSLE, to CrMo's, to Ti, to Al, SS, Ni alloys-GTAW, SMAW, FCAW, GMAW, SAW-manual, semi auto, machine, etc. The space I would need to hold all my welder qual coupons would look like Reliant Stadium. And I would need a staff the size of the US State Department to manage it. No thanks.