Depends which day of the week you are arriving. Generally, if its not a day with an airshow, it doesn't matter. Hit Ripon before 1930 to avoid the 2000 cutoff. During the week, I'd not go too far past noon. This is especially important if you're parking in Vintage (or Green Acres). There are times when we lose the ability to taxi aircraft down south due to some demonstration (C5 arrival or the like) which can mean you'll sit at the other end of the field waiting for the green light to come down.
The other time to avoid is right around 1830 on airshow days. When the field first opens after the airshow, they do departures only until the backlog gets cleared out. Officially, it's an hour in the NOTAM, but it's usually a bit shorter than that.
