I think back to my dads workshop when I was younger and how having kids and getting older must have really caused him to slow down on project work. It seemed there were half completed projects everywhere and many that were never started. I never wanted that for me, so I switched over to 1 single arcade project at a time.
There is a certain amount of juggling of projects I can do before it all falls to pieces. Don't get me wrong, I have an arcade project, but I also have some landscape work, some kids playroom stuff, some car stuff, etc. projects going on, but my arcade is nearly perfect. (I had a mobo die in the jukebox last week that is next on the list).
By having projects completing, there is a sense of getting stuff done for me. If all I could show after 2 weeks of work is cap kits, slots cut, but not 1 completed cab, it would seem like an overwhelming amount of work left to do. Also, an arcade cab has so many projects in it that building one, planned right, takes time.
Woodworking
Artwork design\ordering
Controls (research, ordering, etc)
Painting
customizing the computer
wiring
etc. etc.
Building a single cabinet takes 100% of my time for the length of the project, so there isn't much time to lean or time to save. I've built almost 3 dozen cabs in the 10ish years I've been doing it and I try to get them to 100% before moving on.
Everyone has their own method and everyone can handle half completed projects differently.