I have near ten Series Manager for the BBC.
How can you redo 'em when the series isn't active?
I would leave them in place..... worst case, you'll find out that the series is active again when the first episodes records in SD, and you can change it then. Chances are very high the same episode will be repeated within the same week.
It's probably better to leave them and change them when you notice a recording, else you are going to forget.... a series might not air again till November or so.