Every two years there are changes in design and technology. In the last ten years massive advances in golf balls, clubs, putters, and wedges have allowed us all to have a greater choice for a more enjoyable golfing experience. So those that can afford to stay up with the latest in high tech should change every two years, the average player three to four.
The driver gets the most advertising and interest with huge gains in what goes into the shaft and clubhead. Driver fitting is important no two swings are the same so I would advise off the shelf to be a second and last choice.
Finally design changes effect the eye. If you look down and see a clubhead that you instantly don’t like, find one that suits your eye. The final thing is the feel and sound that the contact is giving you off the club which you are trying. The sound of a solid hit can change everything on the way to making a decision of the clubs you are going to buy.
Buying a new set of irons, fairway metals, driver, wedges, and putter ignite passion to play more. With new memories not old ones that the old set had given. Trusting in yourself with a new set can make a significant difference.