Was just exchanging with KP Keller about this subject, and he had some interesting comments, which he gave me permission to share:
Hard to generalize…
GG is a new name for what has been made seriously like mid/end 80s. Many dry Rieslings from excellent sites still are in excellent shape - wg 1990 Schlossberg Leitz, 1993 Hölle Künstler, 1990 Grünhaus Abtsberg, 1990 brudersberg Heyl zu Herrnsheim, 1990 Saumagen Köhler Rupprecht, 1990 gunderloch rothenberg etc etc
Our vineyards are cooler - we managed first in 1990 to reach 11,5 vol for dry Riesling, 12,0 in 1992. from this time climate change and lower yield helped a lot to get more inner depth and the necessary power to balance acidity.
Next step were the 2000s with outstanding 01,02,04,05(sometimes to soft and a bit too late harvested),07,09 …
After 2015 growers were thinking more about avoiding overripeness than fearing not to reach full maturity- it’s quite similar to Burgundy.
I think good GG vintages have the potential to age for 30,40 years- like good vintages for white Burgundy as well. They can close down when they are young but it’s not necessarily the case…- I would recommend to start drinking our GGs with 5-10 years of age as I think that with a bit of early maturity you get a better feeling for the soil. I would start drinking a von der Fels After 3,4 years - but it can also keep easily 20 years - it depends on personal preference and storage for sure.
I think it’s important to explain that GG is not something completely new- it’s just a new name for sth that started in the early 90s.
Also sweetness in wine does not always guarantee longevity- moderate yields, best soils and give them time in the cellar to develop slowly are very very important facts.
I think climate change helps to get perfectly mature grapes nearly every season - and the good growers have to adapt by shadowing, not trimming, high density plantings, new rootstocks etc.
I think dry German Riesling has never been better and more constant in quality than it is today - 30/40 years ago you needed 15/20 gr of sugar to balance often quite green and hard acidity - today acidity can still be high and phs under 3 at harvesting but the acids are riper and need not be balanced by sugar.
I am a great great fan of Kabinett young and mature - I love natural sweetness that does not really taste sweet any more like 10, 15 years like the best Prüm , Falkenstein, Willi Schäfer - that’s unique in style.
But I also love the GGs with there deeply mineral, stony elegance when they are 10,15 years old and are beautiful accompanying fish dishes, white meat etc