When booking in the last few days before a flight I actually look and see if the exit rows are full and I do think that the chance of their being less elites looking for upgrades is better if the exit rows are empty than if they are full. That being said I think it would be a better indicator on a 757 or an A300 as these plane without MRTC would be more likely for an elite to book the exit rather than a MRTC seat in rows 8,9,10 on a S80 for example. I would not change my travel plans though on a flight of less than 3 hours simple due to my chance of an upgrade. Although I am batting something like 99% in the last two years.