I keep a handwritten journal in my bike shed. Going on 20 years of entries now.
All maintenance on both bikes and cages. I can tell when and how many miles on any tire in a few seconds. Or how many miles/or how much time on an oil & filter or air filter or plugs, or battery, or rear end maintenance. Keep a separate folder with all bills for parts and service (in case I forget to make a journal entry, I can go back and find the info).
All entries have a date and miles.
Pretty high tech, no?


I never take it with me, so it can't get lost. And it's hard to break a book.