I left the oil in both vehicles for ~13 months, both previously changed on Nov. 9, 2010. The Ford went about 4.5 K miles, the Dakota about 5.5 K.
Last week, Dec 6, 2011:
2008 Ford Crown Victoria
32,838 miles
Oil: Motorcraft 5w20, 6 qts
Filter: Motorcraft FL-820S
+ 6 oz Lube Control
Today, Dec 13, 2011:
2002 Dodge Dakota, 3.9 V6
97,924 miles
Oil: Formula Shell 5w30, 4 qts
Filter: Wix 51085
+ 6 oz Lube Control
Air Filter: NAPA 6077