Actually the ammonia test from Aquarium Pharm lasts 3 years. A couple of years ago I emailed AP about the shelf life of varous tests and how to tell if they are old. This is the response I got:
" Each reagent bottle has a Lot # printed on the bottle. The last four digits are the month and year of manufacture. Example: Lot # 28A0102. This is a pH reagent manufactured in January of 2002. Pond Care Wide Range pH, Ammonia, High Range pH, Nitrate, Phosphate, Copper, Calcium and GH all last for three years. Nitrite and KH will last for four years. Freshwater pH(low range) and Pond Care Salt Level will last for five years. I would not trust these kits after they have expired. "