It is like every project in life. You start by researching, learning to put everything together, maintain it, and then close it down and learn from your mistakes. Same can be true to this hobby. The software used to drive it is pretty much complete, then there is the ethics issue of what is allowed to be played on it. New hardware to drive it like the pi, and long assumed dead copyright licenses coming out of the closet with new retro products.
Since the hobby is 20 years old, you have probably moved on with family, work or jail, and you have found something better to occupy yourself.
Yes there are the new devices that awaken that initial curiosity and build, and there are dust covers hiding your last project, with the view to good willing it to someone who is entering the hobby for the first time.
Personally I have way too much in my life to even get my Stargate completed (its all there including the dead boards), and that 1Up is perfect for those one game sessions I have time for. It is just life, and I am sure I am not alone in that situation. Maybe one day if I retire I will get another crack at the hobby again, or by then the 1Up will be that last victor standing.
I'm sure someone will come along and start a new build, or we will see the latest 1Up cabinets and piss and moan about it. It has been a fun 20 years, and we have seen all the arcade games being emulated in Mame and the drama surrounding it. We have seen amazing builds, and learned from some incredible talents in woodworking and graphic manipulation.
I would never in a million years realized how popular this hobby is, and to some extent lucrative, in regards to parts and builds. There is something for everyone, but I too see the light at the end of the tunnel (and it is not someone with a torch), and thanks to Saint for putting up with us and maintaining this site. For what it is, a vessel of information.
There is definitely enough material on here for another book.