Fulltiming has become a term used in the motorhome world for individuals and families who live "fulltime" in their motorhome or RV. It is a world-wide activity, and there are many bloggers who record their day-to-day life on the road.
Many are retired and just looking to do something different and see the world, but it is becoming increasingly common for young families to live, work and school from their home on wheels. This has led to a lot of home schooling.
Individual fulltimers can live extremely different lifestyles. Some may choose to move their RV from one high dollar camping resort to another. Some might volunteer or workcamp in order to trade labor for a campsite. Others might live completely off the grid and boondock (also known as "dry camp") full-time.
These are only examples. Other than living in an RV instead of a traditional, stationary residence, there is no set lifestyle to be a fulltimer. It is a loose term.
There are organizations that represent people who choose this alternative lifestyle. In the US it's the Escapees Club; http://www.escapees.com/ while in the UK. fulltimers have the Motorhome Fulltimers Association http://www.motorhome365.com