Yes, I know - though it's still a good principle to try for. Otherwise all recursive functions would run into stack overflows if the list of calls are long (even if the interpreter/compiler optimizes tail-recursion).
Anyhow, it's a moot point for this scenario. I think the PC might just crash if you have folder paths 20000 levels deep!
One other thing to take note of: The recursive folder listing might take some time if there are 100's (or even 1000's) of folders - never mind their depth. A possible solution is to use dgorsman's depth-limit, see my version of this
here.