Coincidentally, I've been putting a lot of thought lately into doing kind of the opposite of what you're suggesting: I'm considering converting much of my collection back into cash. Our children have nearly zero interest in wearing or possessing mechanical watches so it seems a waste to burden them with stuff they don't want and wouldn't have a clue how to sell properly. There will be a handful of keepsake watches that I'll hold onto, but that's it.
What would I do with the cash generated? Well, I will be transitioning from fully employed to retired over the next couple of years, so it seems fitting at this time to simply convert the proceeds from one hobby into another. For example, there are more aircraft rental hours available from my watch collection than I will ever have time to fully utilize (assuming of course that I don't do something crazy like fly turbine-powered aircraft).
