I have been out of town for the last week. Went to Houston to pick up a used van I bought on the web and drove home (950 miles). There's nothing like a long drive to remind me that sitting is the worst thing for your lower back. It is important to stop frequently, walk around, extend (lean backward) your lower spine, and do some knee bends. Sitting increases the pressure on the anterior (frontal portion) discs tremendously. It is no coincidence that most disc ruptures are posterior (rearward). The increased anterior pressure over a lifetime causes migration of the nucleus of the disc backward. The posterior longitudinal ligament isn't very thick or strong at the posterior margins of the disc and this is where most ruptures occur. Getting out of the seated position and leaning backward helps to relieve that pressure and slow the migration.
Another suggestion is you walk around for an hour or so after arrival at your destination before you lift heavy objects (known as luggage). This hour allows your discs to recover before you overload them with even more pressure.