Sauvignon Blanc, even relatively expensive Sancerre, wines are generally best when consumed young. That said, I always hold back a few bottles of my favorite Sancerre, Domaine Daulny, for a few years because I like the nuances that develop. Yes, crisp gooseberry/cat pee quality that is an important part of Sauvignon Blanc is gone, but Domaine Daulny's vines produce something underneath that is worth waiting for--still finely tuned but complex fruit and mineral flavors that seem to be at their best when the wine warms to room temperature.
This 2007 is a deep gold color now, and I wouldn't want to wait any longer. Still plenty of gooseberry with fresh mint and musk melon. Tamed just a bit from its younger days but with plenty to offer.