Not unusual to see the Tour guys take their time and switch back and forth regardless of manufacture until the get totally comfortable. Lots of money on the line and sometimes "trust" is more important than anything else. As for your last sentence, I think everyone has a point where their old technology could stand to be upgraded, maybe not yearly but I do think my persimmons in the 80's were perfect but glad i am not still playing them now.

It's not always a question of being better or not being better. He has plenty of length so that is not a reason to change. If the dispersion pattern or flight window isn't to his liking, he'd go back. While 5W's have come back into vogue, there are now some 7W's appearing. Mr. DJ is one example. Whatever setup gets the ball in the hole faster.

At this point I can't imagine updating my T400's, SM8's, or Phantom 7.5. The promise of 2-5 more yards isn't as important as knowing what they will do if struck correctly.

Based on the driver fitting I received in 2016, I am still using my 917D2, with a Fujikura Tour Speeder Stiff Shaft. Did go to the T300 irons and R shafts. Picked more accuracy and distance over 918 AP1s. I go to fittings and if no improvement, do not change.

Should say 718 AP1s....brain gas.....

I think where and when to upgrade is a personal choice. I think some pros do it yearly or every two years, and others find something they like and stay with it for quite a bit longer.

I think Bubba had a set of png s-59 irons in the bag for a long time.

If something is noticeably better ( and I mean more than 2 or 3 yards ) then I will upgrade. Otherwise, I stand pat.

I would consider changing my clubs when the time is right. I.e., every four to five years $$$

dustin Johnson has been the best golfer on the planet for the last 8 months, so changing drivers or any equipment was going to be a weird transition. Its typical to see these guys on tour struggle with the change and go back to reliable. Justin Thomas did it in Hawaii when he was originally missing with his TSi, but he has it back now a few weeks later.

For me, with all that cash an prestige on the line, i would want to be comfortable with the club in my hand.

It's so different for those who get paid to play...for some of us switching equipment is more a monetary concern rather than a performance concern. Would a new $500 driver gain me 5 yards? Perhaps but is that 5 yards worth $500?? For me the answer is nope...others answer that question vastly differently.

When I was fitted for the TSi 2, 9 degree driver, I was told by the fitter, right from the get go, that he would not be able to do anything for me because my smash factory was 1.51. I am 77 years old.

I think that you were given some wrong information. Smash Factor numbers for the best players in the world just approach 1.5, with most Tour players under that. I don't think that 1.51 is correct.

You also don't tell us the more important numbers; Clubhead speed, launch angle, spin rate and ball speed.

If you are like most of us, as we get older, out clubhead speed drops. If yours is below 90-95 MPH, I would look at the TSi1 driver. If your launch angles are low (less than 12 degrees) I would look at adding more loft to your driver.

It is very rare that a proper fitting can't find some improvement for you.