Depends on your storage conditions and all, and how much chemicals you use.... sometimes, when you buy chemicals, they simply come in sealed plastic bags, which may be harder to store once you open them up. I prefer glass or plastic bottles, but you don't always get these from photo chemical places unless you buy more than say 100 or 200 grams worth.
Originally Posted by Jeremy Moore
The shelf life of each chemical varies, unfortunately I don't have any info on my at the moment for the different parts of Pyrocat-HD, fixer, etc.
Make sure you buy enough to mix several solutions of stock solution, that way you have more in case you mess up and it gives you enough to test with. Also, chemicals are usually get cheaper per gram when you buy more.