Ilford sells 600mL packages of ID-11 developer. That's perfect for four rolls of b&w film in most manual tanks.(posted 9046 days ago)T-Max concentrate lasts for 3-4 years without noticeable degradation. Rodinal seems to last for a couple of years.
XTOL supposedly keeps in stock solution form for many months when it's in a stoppered, full bottle. Buy collapsible bottles. 1L of XTOL should be able to be used up in a few months at most, even if you shoot little film.
Stop bath lasts forever.
Fixer's good for a year when mixed. Pitch it every New Year's. :)
As for print chemicals, Dektol will keep for six months in stock solution; Ilford Universal and Multigrade developer will keep a couple of years in concentrate form. Pitch the diluted developer after every session; it only keeps a few hours.
Jim