Keep tabs on annual consumption . Stock that going forward times 2-5 when the shelves are full and prices come down .
I use the 1 to try , if it works buy 2 more , when I open the 1st of the 2 I buy 2 more , method . When I get to whatever my target is say 10 for example I buy #11 when I'm using #12 so I have 10 always on hand . It hurts a lot going in but it's sure nice when parts aren't available for going on 2 yr to have enough to hold out for a second term .