It was probably ten years old when I discovered that. When I was trying to find out more about it I came across some DoD regs that require it to last for the life of the uniform which they equated to 50 washings. Even after that it supposedly only losses effectiveness slowly. When I noticed it with my BDUs it was well past the 50 washings mark, so it seems that's likely to be true. It's definitely more effective than the spray-on stuff, that's why the DoD made the switch.