We've sorted the Avalon into generations, which is a collection of years where the Avalon was continuously produced and very few, if any, changes are made. Sorting models by their generation gives us a clearer roadmap of potential problems.
Manufacturers don't always make it clear when a new generation begins, but we do our best to keep our generation data accurate to better predict problems. Use this information as a guide for making your decisions. Or don't (but you really should).