Keep it at least 30 days doesnot make the cut.The federal banking law held the depositor liable for the negotiable instrument up to 6 months .The payer's bank can claim it is counterfeit after you wire transfer the fund oversea if they are part of the counterfeit criminal ring. It is high risk to deposit any m.o or check from person or company you do not know and has no access, in this, the law is not with you.