It depends on how you define "project."
Most people have life goals that filter into professional, personal, family, etc. Some goals might not sound like projects "go on more vacations with the kids," but require a sequence of things to be done in order for them to be feasible.
In "the end," the ones that are most valuable will probably not be the professional things, particularly in the technical space. Most because they'll feel especially inconsequential 10 years out. The professional projects I spent weeks and months on a decade ago are problems largely solved and turnkey in 2016. That said, they're fulfilling, and that's why we enjoy doing them and challenging ourselves.
So unless you're doing some really monumentally important-for-humanity professional projects, their value is probably ephemeral. They should play into a larger set of life goals.