I lend things only occasionally, and to people I see daily or near daily, and I tell the lender that after a month out I will drive you crazy asking for it back.
The rule is more for me than it is for the lendee..I feel no remorse reminding someone for my stuff back.
Funny how success tends to depend on the type of thing borrowed - lending and borrowing tools = good experience; lending and borrowing books, CDs, DVDs = bad experience.