My last travel experience on an Air Miles reward ticket dates from Fall 2000 on a CP itinerary between YYC-YVR-YYC.

I was advised at time of booking, when I called in to the airline to confirm and at check-in (despite being there four hours early) that absolutely NEVER, NEVER, NEVER are they supposed to accomodate Air Miles ticketed passengers on earlier flights. (It was explained that this was one of the terms of the agreement between Air Miles and the airlines)

I went through security and tried one last time with the gate agent. She said she would "try" but four flights left in the intervening period and I was not accomodated...

Can't say if the last three years has made a difference.