Working on a project for 10+ years before it's "ready"

Has anyone had the experience of developing something so complicated that it took ten or more years to complete? I'm not talking about a hobby or a side project, but a full time project that just needed a large investment of time to be actualized. Especially having variables that would be difficult to delegate to others, and/or a lot of trial and error. I am curious whether it was worth it in the end, and whether the time frame was discouraging at any point.