I use a Urinator, and I generally buy Synthetic Urine (Dr. John's Famous Pee Pee). I have some old vials left, but they are quite old (1 is over 2 years old and the other more than a year.) They are yellow still, and have been kept in a dark bag this whole time. I don't want to pay to overnight some more... Anybody have any idea what the worst case scenario would be using the old synthetic? I have a test coming up soon.