I speaking only of shirts with a date on them. I have a 2017 US Open Shirt. I don’t think it’s old enough to retire because of the date, but I also saw a 2002 Ryder Cup shirt on somebody and I thought, really you haven’t gone to one since?
Am I the only one that thinks this way?
Agreed - the 2002 RC shirt has outlived it’s story telling value !
I still have a shirt from The Masters in 2014 that I wear BUT it doesn’t have a year on it and I probably only wear it 2-3 times a year so it’ll stay in my rotation for another.
Wear 'em til they fade, thread bare or just plain wear out.
Not having a date is fine. The date is what always gets me.
I have a nice durable lined windshirt that I received as a golf outing swag. No date, but the two logos are UPS and Olympic rings. Not too hard to figure out that UPS sponsored the Atlanta Olympic Games in 1996. It’s aged a bit better than I have in 25 years 
I have a 1980 Baltusrol US Open shirt. It’s heavy so I still wear on occasion in the spring and fall. It’s in perfect shape too…so there it is. I have a US Open Pebble Beach cap from 2013. It’s in perfect shape. It’s still in the rotation. My Alpaca Red Sweater is from 1980s also. It’s in the rotation. So yea, I buy em to wear em. And continue to. I bought 2 gorgeous 2020 Whistling Straights Ryder Cup shirts from my pro at the beginning of the season for $15 for 2. In the rotation. I’m not advertising for anyone as long as it looks good. I have a ratty PING from 1986 cap that I’ll wear for superstitious reasons at tournaments and will only take it off after a 3 putt…lol
I was almost never retiring them unless there was some stain I couldn’t get out or they ripped. A few years ago I realized my closet was overflowing with golf shirts so I finally started getting rid of them. If I get a new shirt now I get rid of at least 2-3 old ones. I still have too many, but at least it’s manageable again. If I ever retire and play more golf…I would still have too many.
Having a 1980 Baltursrol US Open shirt is quite a different matter. I wouldn’t get rid of that one either. Jack won and I have always been a Nicklaus fan. 
Yea, that was fun, I was there,. Very exciting! Jack just wore down Mr Aoki. I’ve been very fortunate to actually witness some great tournaments. Helped to live where I’ve lived and see some amazing PGA and LPGA championships both as a patron and volunteer.