Contrary to popular techy opinion, short-term memory is not composed of hard, fixed "slots" that fill up and overflow. It's not like remembering one more byte of information will make a variable name fall out of your memory on the other end.

Besides, it might just as well become something you don't need to use memory for at all - just press Esc to make sure. If you're in command mode, nothing happens. If you're in insert mode, you've entered command mode.