Oak barrels are generally used four times. Most winemakers use oak barrels for two main reasons: to add complex aromas and flavors, and to add tannin and age-ability to the wine.
French oak barrels are a critical part of successful Pinot Noir vinification because Pinot Noir loves oak. It is a match made in heaven that gives Pinot Noir structural tannins, contributes texture, adds flavor and builds depth. Oak aging is as likely to bring a Pinot Noir down than to elevate it.