It's a personal choice. There's no way I'd dry mount a print which I intend to keep or sell, wheter my own work or one I've bought or swapped.
Much of my exhibition work is going to a museum, and I also sell prints to collectors etc, as Vaughn says they prefer images to be unmounted.
As I have numerous exhibitioins sets -so far more prints than frames - occasionally mount boards do get damaged, or images might need to be reframe in a different size frame for an exhibition. So now way I#ll go back to dry mounting.