“How long does it take a Solera produced wine to become a different wine?” is sort of an unanswerable question. Presumably it can change over time if there’s a sufficiently permanent change in the inputs, but (presumably because it’s acting as sort of an exponential weighted moving average over the years) I’d be surprised if a new bottling now tastes substantially different from a 2013 bottling in 2013.
In my mind, as the idea of a solera system is to keep consistency and the wine is constantly refreshed with younger wines, it is highly that the wine is very similar in style to that in 2013. I’m not sure how often this wine is bottled but I can’t imagine you would have a bottle from a 2013 bottling…it certainly seemed too fresh to me for that. In saying all that, should TWS be celebrating a champion from 7 years ago?..maybe a refresh of the description needed.
I suppose the other thing to say is that it sounds like this particular wine has had some PX blended in - provided that blending is consistent, then with the comments above about the (relative) stability of large soleras, then I imagine the wine should not change much from year to year.