Bill-
I did a bit more research and still could not come up with a note from adobe on how many custom crops you should be able to save or how to delete them.
I DID run across something I once knew but forgot and it might be helpful to you guys:
two shortcuts.... Shift+A will open crop tool to the last used dimensions and X will switch between portrait and landscape.
Might save you some time when you have a bunch to work...
cheers,
tom