Legacy GM Q:Virtual keys


how do you people handle virtual keys? im really not sure how to approach them and the manual doesnt say much.

for instance, what happens if i set a var to a vkey, then set that same var to another vkey? does it create a leak? does it delete/replace the old vkey? do i aways have to delete the virtual keys when i have to change them? im not switching rooms.
most of the time unless i specify, the game doesnt know which keys to delete and it throws me an error if i try to delete an unexisting key.