One of the main factors in charging batteries when boondocking is the level of the goal. Most folks charge until the batteries are 80-90% charged in a daily regimen. That is because that last 10% takes a long time. This is where solar charging shines as a user can get to that 80-90% and count on the solar getting the last 10% done.
If you are committing to a year of travel, a single 100+W solar panel and small charge controller will greatly benefit your 12V system. When you park in storage, the solar panel can keep your batteries charged so that their longevity is the best. If you look at the ROI of a small solar system vs. the shortened interval of replacing batteries due to lack of charge, the solar system becomes quite attractive.
