Plant food

I, like a lot of other gardeners use both chemical and "natural" plant foods. Straight nitrogen, phosphate, and potash if properly stored will last years. Diluted to a solution they will still last years if kept in a cool dark place. I buy chicken pellets and growmore in reasonably large quantities and again if properly stored they will last a reasonable length of time. Again, like a lot of gardeners, I also use MiracleGro which when, in solution, will last a long time. I harvest cowpats [ I have an affinity for stepping in then when I'm not looking for them!!]
and sheepsh.... which I hang in small hessian sacks in tubs of water until the water is the colour of tea. Now that, after a couple of weeks, will start to smell somewhat - especially if the weather is good and hot. But anyway commercial chemical plant food will last a long time either in it's original form or diluted into a solution.

 

Well, the shop bought stuff in solution usually come in light-proof plastic containers which if you stored them in a cool place. Plant food that come in granule, powder or crystal form will last years if you store it in a cool and DRY place.

 

That's fantastic, PeterS!