poolneophyte, I wasn't answering bats' question, rather I have some unrelated things that bats needs to deal with.
On reagent lifetime: All of the normal reagents will last several years if they are stored properly. You want to store then in a cool dark place with uniform temperatures. They can be damaged by extended periods of high temperatures, lots of direct sunlight, freezing, and by repeated rapid temperature swings.
The FAS-DPD titrant and the PH reagent have the shortest lifetime, still at least three years with proper storage. Most of the rest will last quite a bit longer if you are careful with them. Almost all of them can go bad much more quickly than that if you mistreat them.