If personal property is exchanged for a specific time or purpose, a similar article shall be returned to the lender without demand as soon as the time has expired or the purpose has been accomplished. In any other case, it need not be returned until demanded. The borrower of personal property for exchange shall return a similar article to the lender at the place contemplated by the parties at the time of the exchange, or if no particular place was contemplated by them, at the place where it was at the time of the exchange.