Letting It Breathe

[MontereyRick]

I'm sure the answer to the following question varies depending on the varietal and the age of the wine, but here goes anyway..

What length of time is appropriate for a wine to breathe prior to drinking in order for it to get to its peak?

Sat night, wife and I went to The Whaling Station (great Monterey restaurant) and brought a bottle of 96 Grgich Hills Cab. We had the waiter pop it upon sitting down and proceeded to have a cocktail and an appetizer and did our best to not touch the wine. I'd say at least 20 minutes went by before anyone had a sip. While the first sip was good, it was amazing how much the wine had "smoothed out" (for lack of a better term) by the end of our meal. It seemed as though it just kept getting better and better until there was well... nothing left in the bottle.

Anyway, is there a rule of thumb you experts live by?