How can I make sure that I can revert products back to the original price

The only way to revert prices back to their original price is to make sure that you set an end date for the schedule.

That way, prices will revert at the end date. Or, they will revert when you press the deactivate button.

If you don't have a specific end date for your schedule but want to be sure you can revert prices in the future, just set a date far in the future.