My suggestion: get the "last chance" ones (if they're on your wantlist), if you can/if it suits with shipping costs, add something else (I just ordered both running low ones and threw in the Carter/Bradford Select to get the order just under 300$)... and if you have some extra cash, get some of the not yet running low/newer ones.
I've done so in the past few years, have bought the Crusaders, Ellington Small Group, Chu and Braxton from the in-print ones (lots of it not played yet) and managed to get hold of almost all the "last chance" ones in time.
I tend to only buy them when they hit "Running Low" as well. Somehow I can justify the expense then. I also always throw in a Select when I buy a black box because what's really the difference between $120 and $165?
Yes, the key word here is 'rationalization'