I rarely use it, but I have know people that used the "natural" stuff for several years. Long before someone came out with a "Recovery Kit" for that a buck's urine a friend had been doing it for many years.. Often he would recover urine this year and not use it until next year. The urine was stored in a half gallon jug, he may have some left from the previous year and put the newly recovers urine in the same jug with it. He always had several scrapes, and drips in the area and they seemed to work. I remember a drag he gave me that had a wound up piece of burlap attached to a 4 foot piece of parachute line that was stored in a fruit jar filled with his recovered mixture. I tied it to the rear bumper of my pickup and drove to stand one morning, and I will swear, I watched at least eight-ten bucks pickup the trail and walk within range of the stand, a couple of them came up to 5-6 feet from the truck sniffing for the scent.
Commerical urine likely has additives that may affect the shelve life, and the natural urine may also "expire", but from my experience it didn't seem to hurt it.
