I buy it if I think I'll need it (and sometimes when it's just something I have to have
). I try and plan a few weeks ahead so if I'm doing a task and the Tool man doesn't have it it'll be here in time. I attend Storage Sales, and I've bought a couple of completely full roll-aways, air and electric Tools pretty reasonably.
I do have some HF stuff (mostly for those one or two times uses), but I generally will buy top of the line stuff if I'm keeping it for long-term continuous use.