One of the projects I am currently working on is restoring an IBM ThinkPad 701CS (https://blog.jgc.org/2023/03/repairing-tiny-ribbon-cable-ins...) which has required a total teardown and rebuild. I started this project in early January and currently have a working machine that's in parts. I work on this when I have time. Which might be for two or three hours a week maximum. Basically, I decided to get satisfaction from small improvements. So, one time when working on this I just cleaned up the battery contacts, another time I replaced the CMOS battery and saw that it was retaining RAM size, another time I repaired the keyboard, another time I just sat down and figured out which parts of the case I needed to 3D print to replace, etc. etc.
I usually have two to three projects ongoing and just pick them up when I have time and inclination.