Yup. I've been tracking it since 1988. I write it down in a Week-at-a-glance calendar and I have every calendar in a file drawer. I transfer the data to a spreadsheet at the end of each year and I know my mileage...both commuting and recreational...for the entire period. I know exactly (well a very good estimate) how much gasoline I haven't used (8784 gallons), how many tons of CO2 I've kept out of the atmosphere (47 tons), how many days I've ridden to work (3617), what percentage of work days/year I've ridden over 28 years of records (49%) and I even estimate how much soap I've used in my morning shower over 28 years (174).
Obsessive? Yea.