Each time you create a sale, the sales price will be saved in a historical field per product / variation. When a sale is over – prices and sale date (s) are deleted, you can easily set up a new sale with the previous sale price. A function that makes it quick to set up your recurring sales. Just use the bulk function on sales price > Get previous sales price (a bulk insert is done to any visible row with a previous sale price).
Sales prices is now equal to your previous sale, just fill the new dates (optional) and you have a new sale running. Remember to save.