Jadot acquired the property at Chateau des Jacques only in 1996 so the best we can do is talk about a 12 year history of the specific wine, prior to that, if memory serves, the grapes of the property having gone to Domaine J. Thorins, the wines being made quite differently and often categorized merely as Beaujolais-Villages.
There are five clos in all under the rubric of Chateau des Jacques – Thorins, Grand Carquelin, Rochegres, La Roche and Champ de Cour – and in addition to the "regular" Chateau des Jacques release Jadot also occasionally releases single wines, that depending much on the quality of the harvest in different areas as the clos are not continugous. Under any label, however, the wines have shared certain commonalities since the 1996 release –being meatier, more full and more robust than most other Moulin-a-Vent wines and, in fact, more than any other Gamay releases. In their youth (the first two-five years after bottling) the wines do have what I would call a "Gamay plus" nose and palate – that is to say distinctly Gamay, clearly Beaujolais cru but with an added level of depth and fatness that shows that these wines will develop far longer and far better in the bottle than their Gamay brothers and sisters. As the wines come to maturity – generally somewhere between six – ten years after the vintage, their extraordinary structure and fruitiness show fine balance and indeed the wines become more "mellow". In that we are fully agreed that one can easily mistake a mature Chateau des Jacques for a fine Cote de Beaune.
As to evolution over between vintages, what I have noted are moves towards a somewhat more floral nose (rose petals and iris), somewhat fuller body (that seeming to level off nicely somewhere about 2003), and a more velvety texture on the finish. Overall, the wine has held its consistency well, showing fine balance between red fruit, crisp acidity, spices and its meaty nature.
I do, by the way, agree with Hugh Johnson that in a meal based around Beaujolais cru wines that this one should always be served last, ideally with a cheese course, as its weight and structure would overshadow other Beaujolais wines if served too early in the meal.