Jimmy Deignan's first time was with a $500 portable DVD player. He bought it a few years ago at Best Buy for a Boston-to-Los Angeles flight, knowing he would return it for a full refund when he got back. More recently, in November, rather than spending $600 to rent a LCD projector for a business presentation, the Holden resident purchased one at Staples, then returned it a few days later and got his money back. The way Deignan sees it, he is just a smart shopper: He gets the things he needs, uses them for as long as he wants,...