Every other year I start looking into what new technology there is. Clubs like my driver and fairways I change pretty much every year since there is always something new and wonderous.
Irons are a different matter. Until I start skanking it up out there, I really don't like to change. This year I did go out and pick up a new set of irons, since I couldn't nut a darn thing. Also adjusted my wedges at that time.
As for putters, a whole different story. In the last 12 years I've only used 2 different putters, both Cameron's. The current Delmar that I have is a wonderful club, and there is no way she is being removed from the bag. Love my putter.
I don't rush to change unless I can see a real difference when I use the new fangled club. Now I have the benefit of living in California, where every practice facility has a set up for most brands to demo. My club is a TM fitting center, so I can use any of their technology on any given weekend, including taking a club out on course to try. I know some of you can't do that, so it is hard to know what to get. As many will note, using a good club fitter is the key to good results.