I take on projects in or leading up to the dark, rainy winter months, most often - and with projects come buying needs.
This year, all C&V bikes are built and rolling, funds are low, and there's little room for additional projects - my only buys, barring something really exceptional coming up, will be bits to build up a brand-new Lynskey Cooper frame that just came in (budget dictates a 3-4 month buying schedule for fork, hubs, and a few other items). But that's a bit of a departure from my 'habit'.
As a rule, I'm typically year-round.