Central to the Spanish winemaking philosophy is the belief that wine should be released only when it is ready to be consumed, and not a moment before. Spanish wine law focuses squarely on this issue: the terms Crianza, Reserva and Gran Reserva are highly regulated indicators of the amount of time a wine has aged prior to its release. In Rioja, Navarra, and the Ribera del Duero (which have the most stringent requirements) red Crianzas must be aged a minimum of two years; Reservas, at least three years; and Gran Reservas, five years. Of course, top producers will often age their wines far longer than they are required to - sometimes decades.