You've sumed it up pretty good...
All of my 70 something segments on CP last year as well as 50 something segment this year were upgraded by the day of departure, only twice did I have to standby for an upgrade at the gate. On the 4 QF flights and 2 AN flights, I have not been upgraded. Getting upgrade plays an important part in my decision to go for mileage run(s) to get top status. MRLIMO described it well... it's an investment. An investment put in now to get the upgrades for next year. The $$ put in for mileage run is usually the value of an upgrade from Y to J on a single international trip.