Whilst serving in Borneo a young private, supplemented his personal items of toiletries, by writing to various manufacturers of said products, praising their durability and usefulness etc. in the hot, humid climate of the jungle.
Invariably he would receive a reply and a small parcel containing samples of the product, which he used or sold to his mates.
A junior RAF officer heard of this wheeze and decided to try it. He wrote to Gillette, telling them that he'd been using the same blade, in the jungle, for a year and it was as good as the day he bought it. Gillette replied, thanking him, saying they had great pleasure in enclosing another year's supply!