I get this questions a lot. My answer is generally the same. If you are playing golf frequently and it is a big part of you life you should try and stay up on the latest equipment. If you only play a couple of times a year and do not see that changing in the near future don’t spend the money.
If you are an avid golfer you should look at Drivers and Fairways every couple of years. This does not mean you have to purchase, just compare the new gear versus what you are playing. If there is no huge improvement, then wait.
In regards to irons, I generally suggest every 4 to 5 years. Again, I am not saying you have to purchase new irons, just compare them to the new models and see how your current set stacks up.
If you are flush with cash and love having the newest gear, have at it and enjoy!