My longest trip was to Beagle Point and back, as part of the Distant Worlds Expedition. The entire trip took ~4 months. If I was in a hurry to get to the next waypoint I often just scanned the main star and any other nearby companion stars. Sometimes I'd also scan interesting or valuable planets. To break things up, I'd sometimes scan the entire system (including moons, but not belts).
When I sold my exploration data, I went from Pathfinder at 60% to Pioneer at 61% (completely skipping over Ranger) and earned over 106 million credits. After a short break, I went to Jaques Station in Colonia for a CG and when I got back to the bubble, I reached Elite rank (and got a whole bunch of first found systems and planets).