For many tasters, even the most experienced, the idea that Beaujolais can age comes as a surprise. Our assumptions about the longevity of these wines are largely coloured by our expectations of simple Beaujolais, or even Beaujolais Nouveau. But while both of these typically fade within months of bottling, wines from the region’s cru zones – and even the best of the villages – can far exceed this brief life span.

The factors that help to predict the drinking window of the region’s top wines are manifold (as they are elsewhere) and include yield, winemaking and terroir. Clearly, the lower the yield, the more concentrated the wine – and with that concentration comes a greater probability of long-term survival. Winemaking, too, has a part to play in helping wines to age. Wines made with a brief low-temperature semi-carbonic maceration, or those made with thermovinified grapes, tend to be simple, fruit-driven styles without the structure for long-term maturation. (This is why those basic Beaujolais and Beaujolais Nouveaus are unlikely to make it for the long haul.) But the use of Burgundian winemaking techniques (using destemmed grapes and extracellular fermentation rather than the semi-carbonic maceration typically employed in the region) or allowing for a greater degree of tannin extraction in a semi-carbonic fermentation (there are various methods by which a winemaker can achieve this) can enhance the ageing potential of a wine.

The trouble with relying on winemaking as a predictor of longevity in Beaujolais, though, is that producers rarely – if ever – give wine lovers any indication of how their wines were made. And yields are never printed on labels. So for most of us, the most reliable indicator of ageability in Beaujolais comes from terroir. The sweep of pink granite that runs like a spine through many of the crus tends to produce fine-boned, elegant wines that nevertheless have the structure to age. These soils dominate in Fleurie and Chiroubles, and they are present to a high degree elsewhere, most notably in Moulin-à-Vent, and in the western sectors of three further named crus: Morgon, Régnié and Brouilly.

The most famous vineyards of Morgon, however, are those of the Côte du Py, an outcropping of diorite, a hard, blue-tinged volcanic soil whose wines are typically rich, concentrated and structured. This diorite is also found extensively in the crus of Juliénas and the Côte de Brouilly, which show a similar potential for longevity.

The ageing potential of the village wines is somewhat untested at present, but the best villages – places like Lantignié and Blacé – often share similar geology to the crus. Further, their frequently elevated altitude, once a liability in an era when growers struggled to ripen their grapes, can lend freshness and tannic grip to the wines. The combination of these factors may well presage increased ageability.

With the region’s producers showing a greater degree of confidence in their terroir – and a growing appreciation of the qualities of top Beaujolais – maybe it won’t be all that long before tastings of aged crus will come to be seen as the norm rather than an occasion for astonished surprise.