Ping has a roughly 18 month product cycle. A little longer than others. I like my G driver / fairway woods / irons, so I'll stay with those. Won 1st place in our Quota game yesterday and last Friday with an 80 and 79.
As was said the improvements are so miniscule that it makes no sense to change. I still have my G15 irons which could be put in play and not miss a beat.
I did put a Flat Cat putter grip on my Ping Bergen that worked well yesterday.
I'm smoking my Ping G driver. Measured 2 drives yesterday with my GPS. They measured 233 and 238. Not bad for a 62 year old with a 90 mph swing speed.