That you seek out some unusually mature wines may have something to do with your combined role as scientist and intellectual. Commendable but leading, I must say, to some fairly "weird" wines.
The Brane Cantenac was a great wine not only in its youth but in its maturity as well, holding quite nicely until its 50th year but somewhere shortly after that the wine went on to puppy paradise (that place to which all fine wines and good dogs go after their demise in order to frolic youthfully forever). The 1955 Las Cases was never a superb or even excellent wine. It did go on rather nicely until the mid 1980's but that was indeed its limit. My most recent tasting notes for both wines follow. As you will see, at those final tastings, I was not impressed.
Curiosity in such cases is commendable and I never question that. What I do question are the intentions of those who wish to sell such wines.
Chateau Brane Cantenac, Margaux, 1947: In its youth and until its 50th year a full-bodied, deeply tannic but exquisitely balanced and well-structured wine that showed layer after layer of blackberry, currant and black cherry notes, those with generous earthy mineral and peppery overlays. Now, as happens with all good people and all good wines, returned to its maker and no longer drinkable. No longer scoreable. (Re-tasted 3 Feb 2001)
Chateau Leoville Las Cases, St. Emilion, 1955: Always a bridesmaid and never a bride, a pleasant little wine in its youth, showing medium-bodied, soft and round with appealing berry-black cherry fruits but always just a bit one dimensional. Now well past its peak and maderizing rapidly. No longer scoreble. (Re-tasted 24 Aug 1988)