Hey, Chuck:
None of this would be a big deal if it wasnt so hard to remember to change the date on a note, and so irreversible!

That said, I think it would depend on what is going into the prep note.
As we discussed, for a prep note prior to an initial visit, where you are entering a large amount of data, I do think it is reasonable to save that note. But I agree with you, that if you did that before every encounter, it would create a lot of clutter.
If you're going to have a similarly large amount of data prior to the next encounter, I don't know what I would do.
However, if I just wanted to create a to-do list prior to the next encounter, or wanted to fill in a little HPI information before the next visit, I would consider creating an email text message and either saving it to their chart, or forwarding the email to myself for review the next day.
If you save that data to their chart, then that saved email will pop open like an alert before their encounter screen appears, to remind you about this data which you have entered. The new note will of course come up with today's date, automatically.
The prep data will be available under the Past Encounters tab, in the form of a saved email, and you can cut'n'paste info to the new encounter note, as needed.
If you're worried about cluttering the Past Encounter tab with old messages, they can be filtered out of the display using the radio buttons on the right.