I Take 6 Mg Warfarin Daily Because Of Multiple PE

I take 6 mg warfarin daily because of multiple PE in both lungs at the same time. Also have been diagnosed with DVT. My right calf is already larger than the left and when I sit for periods of time with out moving, my right calf swells even more. My question is, How long is it safe to drive before taking a break to stretch my legs?