How long until I can throw out an unclaimed items sent in for repairs to my store?

First, read the receipt that you gave the customer(s) for the items that were left at your store in that the terms and conditions of the document will set forth the time period as to how long you can retain the items before disposal.

I suggest that before you discard the items as a safeguard, you send the customers written notice of the need to pick up the property within a certain time period. If not picked up by the stated time period, you can then dispose of the items.