As I wrote in another thread I tested the two Leslie blue box test kits side by side, one is freshley bought and one is 10 years old (2005). The only different reading was FC, and I suspected the #2 chemical. So tonight I tested it using #1 from the old kit and #2 from the new and the reading came out exactly the same.
So, in 10 years the only chemical that aged sems to be #2.
Again, cannot claim anything, if anyone is interested how it was kept, it was kept in my garage where it is never really hot. Closed.
Make of it what you will.