They're not supposed to care. They just hand you a new set if you have the old. Every once in awhile an employee on a crusade thinks this is "wrong" but it's fine by company policy -- contact the regional mgr if necessary.Silly question. How do warranties work on wear items?
In many cases you can buy a new set today and return the old set later for a refund. Verify first, though. This is actually how most commercial warranty is handled -- buy today, send the old part back with the driver and get a refund tomorrow