Kodak's current recommendation is 18 months from date of manufacture. Production date is on each bottle as a 4-digit number consisting of year and week of the year. For example, '0648' would be the 48th week of 2006. General consensus is the developers have the shortest life span. When nearing the end of the kit, you might lengthen the bleach time a bit to insure complete bleaching. Do a thread search - there is more discussion on the subject.
Good luck.
Bob