For wine lovers, Mendoza [1] alone merits at least a week; even those with only a passing interest in the vine should spend a few days, ideally during the March Vendimia (harvest festival, when reservations are almost obligatory).
The upper Río Mendoza valley [2], en route to Chile, is close enough for recreational activities like white-water rafting and even winter skiing, though there are also accommodations at the slopes of Los Penitentes [3]. Wine aficionados can extend their stay to Uco vineyards [4] and San Rafael wineries [5], to the south.
Whether hiking or climbing, Aconcagua [6] is a trip in its own right. A three-day hike is possible, but the trek to and from base camp is a 10-day commitment, and climbers should budget three weeks for a summit assault—whether successful or not.
Visiting the desert parks of San Juan [7] and San Luis [8], plus La Rioja’s Talampaya [9], would ideally require a week because of the distances between them, even given only a day at each unit (plus a recommended detour to the Difunta Correa shrine [10]). It’s best to avoid these areas in summer’s heat, when rare storms can cause flash floods.
Córdoba [11]’s urban attractions are independent of the seasons, and its Sierras [12] are popular throughout the year (but crowded in summer). Many visitors cross back and forth between Córdoba and the Sierras of San Luis.
Links:
[1] http://www.moon.com/destinations/argentina/cuyo/mendoza-province/mendoza
[2] http://www.moon.com/destinations/argentina/cuyo/mendoza-province/the-rio-mendoza-valley
[3] http://www.moon.com/destinations/argentina/cuyo/mendoza-province/the-rio-mendoza-valley/los-penitentes
[4] http://www.moon.com/destinations/argentina/cuyo/mendoza-province/mendoza/sights/wineries-the-valle-de-uco
[5] http://www.moon.com/destinations/argentina/cuyo/mendoza-province/san-rafael/wineries
[6] http://www.moon.com/destinations/argentina/cuyo/mendoza-province/parque-provincial-aconcagua/cerro-aconcagua
[7] http://www.moon.com/destinations/argentina/cuyo/san-juan-province/san-juan
[8] http://www.moon.com/destinations/argentina/cuyo/san-luis-province/san-luis
[9] http://www.moon.com/destinations/argentina/cuyo/la-rioja-province/parque-nacional-talampaya
[10] http://www.moon.com/destinations/argentina/cuyo/san-juan-province/san-juan/sights/difunta-correa-shrine
[11] http://www.moon.com/destinations/argentina/cuyo/cordoba-province/cordoba
[12] http://www.moon.com/destinations/argentina/cuyo/cordoba-province/sierras-de-cordoba