"STORAGE You can store working-strength solution in a full, tightly closed bottle for six months, in a half-filled bottle for two months, or in a covered tank for one month. You can store the concentrate for up to two years."
like with any developer, your film won't develop.
you need the right ingredients that is about it ...
wrong ingredients ... well its like trying to make steak tips out of brussel sprouts ..
if this is your first film development, as i and others have said before, it might be less nerve wracking
if you use a store bought conventional tried and true developer to make sure you have your technique down ..
and that way if things go-bad you realize it is technique or camera realated, not because you used caffenol ...