I juste received my last portion og GG wines from 2013, our wedding year. I have drunk several GG wines with 7-10 years of age and they were all showing at apogee (Breuer, Kuhn etc) but how long could you age GG rieslings? I have for 2013 mainly bought Donnhoff, Schäfer-Fröhlich, Wittmann and Keller. Could they go for our 25th anniversary (we have Mags too)? 
Any insight is appreciated!
Not sure we really know, except that GG are really just Spätlese/Auslese trocken in a fancy bottle. Those age just fine for 20 years plus. I have had some early '90s trocken wines that are still going well if on a bit of the far edge of maturity.
How come some Spat/Aus can last 50 years but GG at 20 years are on the far edge of maturity already?
The balance between sugar, acidity, and alcohol is very different
Sugar is a great preservative.
And I did not say near death at 20, just beginning a long, slow decline.
Also, on those old sweet wines, there was probably a heavy dose of sulfur!
I don’t necessarily disagree with aging potential of 20+ years but I do wonder if they will actually be better/different.
I am guessing based on early GG’s and Spatlese Trockens that after 7-10 years the evolution of GG’s will stop unless in large format.
10 years seem to be a safe option based on my experience with wines with up to that age on them.
There was a long thread on this topic a little while back with some very good perspectives.
It depends on the GG. I’m sure some will age quite well, but not all.
I’ve tasted a number of dry Mosel Rieslings that have aged a long time, even trocken (dry) Kabinetts and QbAs.
Almost all Grosser Ring – VDP Mosel-Saar-Ruwer producers avoid the heavy, extra-tall GG bottle, which either has the embossed or engraved “GG” on the glass. (The “Erste Lage” embossment was used before the VDP came up with Grosse Lage.) Reichsgraf von Kesselstatt uses the one with the embossment; Dr. Loosen has one with the engraving. Others use just the taller bottle with “GG” on the label.
Is the sulphur use these days much reduced in Germany?
10 years would seem conservative, the trocken ‘estate’ rieslings from some top producers need already 7 years to open up a bit to my taste. But again the winemaker will make the big difference, eg. Nonneberg 2002 from Brueur was teriffic in 2012, I have now only from 2007 onwards some bottles and these I don’t dare opening yet.
Depends on who you ask. Rovani thinks the German vintners are using illegal levels. Of course he never offered any proof.
In general there is less than their used to be, but still a good bit in the sweet wines.
By “stop,” I assume you mean head down hill, yes? German Riesling is a category I am so woefully uneducated about.
I would agree for most wines. So far, there are very few that - in my opinion - benefit from or are in need of longer ageing: Bürklin-Wolf Kirchenstück and Jesuitengarten, Koehler-Ruprecht Auslese Trocken “R”, Breuer Schlossberg, Emrich-Schönleber Halenberg (although this is usually great at all stages). I’d presume that that list will be getting longer when there’s more experience with these wines aged. I’d say that the wave of very high quality dry Rieslings from Germany in a richer style only really took off with the 2001 vintage (so that’s not even 15 years ago). And some producers that are highly regarded today like Schäfer-Fröhlich, Battenfeld-Spanier, Peter Jakob Kühn, Wagner-Stempel needed some time to find their style (or are still in search of their style), so it won’t be until in a few years that it will be possible to say how they develop.
The answer is very simple: no one knows. And I don’t mean this lke “no one can know the future”. Even those producers who used to make ageworthy Auslese trocken or Spätlese trocken (Karthäuserhof, Laible, Bürklin-Wolf, Breuer etc) might have changed techniques in the last years.
Markus Molitor has a long track record of making long-lived dry Mosel Rieslings. I’d add Maximin Grünhaus, too, even if some only like the sweet wines at this estate. Martin Müllen also has impressive dry Mosels from back vintages.
FWIW, Gilman suggest drinking windows for Keller’s 2013 GGs from 2022/23-2065/75!!
I like that John Gilman has drinking windows for Kabinett trocken beyond five years.
I have long wondered this question as I start to collect more and more GG’s. Just picked up some Von Winning GG’s and wondering when they will be reaching maturity and how long they will hold.