It seems like the best thing for you to do is to invest in some Quick Fix 4.2. That stuff can be used and warmed over and over without any harm. Human urine is different. The specific gravity tends to break down faster after repeated freezes and thaws. Since human urine is good at room temp for approx 8 hours, that would be a consideration when determining how many hours it had been at room temp.

EDIT: Just wanted to add that human urine is good in the fridge for up to 5 days and in the freezer for about a year.