All of our driving has to be completed in 14 hours (11 hours driving total). When I drove over the road (not home every night) I usually tried to aim for a leg stretch every 4 hours. I'd usually walk around the rig and check things out for leg stretchers. For the 30 min break I would find a rest area or a truck stop and have a proper meal and I usually took longer than 30 for that break unless the place was boring. When i would take breaks were usually determined by location along the route.