Taruzake, matured for a short period in cedar (sugi) barrels is a very traditional style of sake dating to the Edo period, when barrels were used to ship sake from Hyogo to Tokyo. The cedar infuses deep flavors of citrus, pine needle, black pepper and vanilla. Taruzake is a legally controlled term, and must fit certain criteria to be named as such.
But with all sorts of wooden casks, fermentation tanks of various sizes, and wood sourced from this forest or that, this part of the tree or another... the creative options for taruzake are limitless.
This category includes both taruzake (a legally defined product) and wooden kioke-fermented sake: a close cousin with a much milder flavor.
As a flavorful style, shelf life is long: at least 6-8 weeks. Always taste sake before throwing it out! Old sake will change, but not necessarilyin a bad way.