I really don’t know about suede. I have only worked on this one bag. What I am impressed with is that it went though the washer with no problems. And by the way, I picked up this nail brush to brush my bag with to hopefully keep dirt from getting embedded.
Regarding vintage glove tanned leather bags, that may depend on the age and condition of the bag and leather. I have a flap bag, I believe made in 1996 that was my experimental bag that I dunked once or twice and then dunked again after finding tPF. It was in good condition to start with and multiple dunking shave not affected it. I have several bags I would like to redunk when I can, for various reasons. My vintage dunking experience is basically with bags 15 -25 years old.
When it comes to bags that are 30-40 years old, which I don’t have experience with, all bets are off and other opinions are welcome.