How often is a passenger jet aircraft painted?
As always, it depends. From what I've seen and read, it's usually redone every 5-10 years. This can vary on various factors from paintshop availability, to new color scheme rollout, to deterioration of the previous one due to bad painting, to quality of the paint used. Sometimes, special liveries are just an aviation specific sticker that's put onto an aircraft, other times it's fully painted onto the aircraft, just depending on the airline, the planned length of time for it to be special, and any other considerations.