Dave,
Speaking only for myself, I've been shooting 35mm for a long time and LF is new to me. I wouldn't even be able to afford it if it weren't for used equipment, including holders. I had a problem with one holder in terms of a light leak, but I couldn't tell which one until after I ID them (in my case with notches and binary numbering). After numbering them and using the offending holder again, I was able to trace back to it easily. It was a hairline flex crack in the dark slide. So, that's situation where it helps.