"A five year criminal statute of limitations applies to all money laundering violations of 18 USC §1956 and 18 USC §1957. The five year statute also applies to violations of 18 USC §1960 absent any other specific provision. The statute of limitations runs from the date on which the money laundering offense was completed".http://www.irs.gov/irm/part9/irm_09-005-005.html#d0e64
so if the money launderer only receives bitcoins and never spends them until 5 years has passed, wouldn't it be a.) be hard to prove guilt b.) cause the money launderer to go insane during those five years from fighting the temptation to spend as the value skyrockets?