For me it was a combination of 1 & 3. I can't claim 2 because I've been tracking how many books I read for the past few years. However this year's goal, 50 books, was always going to be a stretch given that last year I managed 30 and the year before was 18!
I found I can maintain a level of reading that'll get to me to 50+ only if my motivation remains high and there were times when I was too tired or too fed up to feel like doing anything much more than slumping in front of the TV or PC.
Re: "free-range" reading - I never used to track these things but then having been an avid reader when I was young and realising with a shock one day that I'd only read about three books in the previous year, well I wanted to consciously change that and so I started measuring. (Plus there's a geeky part of me that likes all the numbers etc)