Well I have to disagree with you on store bought urine being ineffective. As far as how long they last, this I'm not sure of. Buck bomb makes a scent with a protectant in it to preserve the urine. Scent is a combination of several proteins interacting with excreted chemicals in urine. There are also many enzymes in urine which have the net effect of degrading the proteins that comprise the scent package. Scent Protect deactivates 31 different enzyme systems protecting the proteins and allowing the scent to remain potent and viable for extended periods of time. Additionally the scent package is affected by a change in Ph of the animal urine due to break down products in the urine and either primary or secondary contamination of the urine by bacteria. Scent Protect TM stops bacteria growth and as the bacteria die the active chemistry inactivates the enzymes contained in the bacteria and stabilizes the Ph factor in protecting the scent package. Here in the northeast two days ago, last day of archery only season, I used a estrous scent and brought in a curious spike. He had his nose to the ground coming right up the scent line I put down. He was 15 feet from my stand and I let him go.