I was fortunate enough to taste a '93 Ridge Geyserville Zin in January at the ZAP Flights event. It was absolutely wonderful with some very interesting flavors that I haven't really had very often in a zin. It had flavors which reminded me of brown sugar without the sweetness. It also had some very nice stewed fruit flavors as well. I'll dig up my notes and post them here. There were some other "older" zins there, but the Ridge was the best.

Have you tried Nalle zins. Doug makes his zins to age. We recently opened a 1998 and it was outstanding. I like my zins younger but he makes classic style zin. Below is a SFGate article on Nalle.
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/01/18/WIGVUALQP.DTL

Fanucchi Vineyards makes that great traditional style too: balanced to age. It is too bad that the big "critical dictators" ignore these balanced styles of Zin. For example the Fanucchi Vineyards is 1998 is still outstanding. ...But those guys won’t consider that because they declared that to be a "Bad" vintage. If you can't locate a Fanucchi Vineyards 1998 the 2004 is fantastic now.