It really would depend on what you're doing, but in my experience, the only time an extra line is needed is when you're completely done editing.

E.x. let's say your replay is 500 frames long, on the line of code that begins with
asdf code:
or whatever it is I forget exactly, you don't add a space after every line. Merely after the very final line in the replay, which should be either CRUSH or LINVEL.
I've never seen adding a space in the middle of a replay code cancelling out what is before it for me. idk


Also, leaving the final space line blank saves a tiny little bit of space. It's not much, but it's a bit :L