Why wouldn't a urine sample be good indefinitely without refrigeration? They're sent to labs through the mail all the time.

Here are some things to think about. Since the less we consume of something, the quicker it passes through our body, maybe you can try to cut your intake. Also, marijuana home tests will let you know in advance if you will pass with your own urine that day. (www.professortestkit.com is one of many sites where you can buy some.)

But, bottom line for me would be: I'd rather fail a drug test than get caught cheating.