If you activate the Oxine, it is only viable for 7 days (you can possibly push it to 10 days). However, it has to be kept in an opaque container during this time or it will degrade rapidly. If you do not activate it, as long as it is kept in an opaque container and not exposed to sunlight, it should be ok until the Oxine expiration date, printed on the gallon container. (Because all you are doing is diluting it.)