Under accrual-basis accounting, warranty expenses are typically estimated and accrued in the period when the sales are

Question:

Under accrual-basis accounting, warranty expenses are typically estimated and accrued in the period when the sales are made. If you were in a position to set income tax regulations, would you allow companies to deduct warranty expenses at the time of the sale, or would you make the companies wait until they have actually provided the warranty services? Why?