Zenith Defy Classic Tourbillon Men's Watch 86.0526.4035/21.C648

One of watchmaking's major trends is the mean extension of movements' operating autonomy. Records for watches with the largest power reserve have been successively shattered as new heights have been reached. In parallel, this field has experienced another, more discreet, more widespread and far more useful change: calibres delivering 70 to 240 hours' power reserve have never been so plentiful and so inexpensive.

45 hours was the longstanding norm, meaning barely two days between a watch's maximum state of wind and the moment it came to a halt. And even then, rating precision was far from satisfactory during the last hours of that period. This implied a failure to cover the psychologically important span of the weekend running from Friday evening to Monday morning, and yet this point of reference translates a genuine need not to have to rewind the watch when beginning the working week. The underlying idea was that people would meanwhile wear their 'weekend watch' for gardening or sports activities.

Models with more than two-day power reserves were expensive and sometimes downright exorbitant. The 72 hours generalised by A. Lange & Söhne, and the eight days that had become a speciality of brands such as Chopard, Panerai or H. Moser & Cie: all these fine, comfortably autonomous mechanisms carried hefty price tags. But things have changed, first and foremost due to the emergence of a new generation of of calibres adopting 60 to 70 hours as the norm. Not all of them are expensive, as proved by the H30 calibre used by Hamilton: getting 80 hours' running time at the brand's customary prices is a real bargain. When Tudor launched its in-house calibre, it did so while packing 70 hours under the bonnet. Prior to that, Chopard had already given its 01.01-C base calibre a generous 60 hours. While sticking to reasonably priced segments, these brands had thus managed to house larger barrels equipped with longer mainsprings inside their movements without hanging customers out to dry.

The trend also extends to the upper end of the market. Hublot's proprietary Unico movement boasted 72 hours right off the bat. The new Zenith Calibre 6150 ensures 100 hours thanks to its two barrels. While it doesn't come cheap, it represents a key step in this direction for the first significantly evolved version of the brand's Elite movement line in more than 20 years - thereby reflecting an inexorable groundswell in the industry at large.

Admittedly, a seven- or eight-day power reserve remains a prestigious asset for the brands that are accustomed to providing such a comfortable duration. Such is the case with Bovet, which had already acquired the habit of building its in-house movements - generally comprising sophisticated complications - to this standard. It therefore comes as no surprise that its first incursion into the field of base movements (if one can reasonably apply that adjective to such a calibre) should be a double-face 7-day version with reversed hand-fitting. The ultra-thin Manufacture Bulgari calibre named Finissimo, measuring just 2.23 mm thick, provides 70 hours of autonomy, mainly due to its sheer width that compensates for its diminutive thickness.

The trend is definitely spreading, since Panerai's P.5000 calibre achieves an eight-day power reserve (a nod to the brand's historical calibres) and is fitted in models that cost the same as others with only three days. But Oris has definitely sprung the biggest surprise with its Calibre 110, equipped with a single barrel yet ensuring 10 days' running - and all at a very attractive price. Will that be enough to force more prestigious brands to rethink their pricing policy?