You can run the Cummins longer, but while its under warranty I wouldn't push it. Even just sitting oil can degrade, I know guys who run their Cummins over a year without a change and the oil still tests good. With my Cummins I usually stuck to a 6month change schedule.
2013 Ram 1500 HEMI BigHorn quad cab silver 6speed 3.55AntiSpin
Rock River Arms Operator 2 Equipped.