When I tried for The Ultimate achievement I ran a non-ToI character alongside the ToI one and I noticed that my load times were becoming far longer on both characters as the game progressed. This had not been an issue in previous ToI playthroughs indicating that the size of the loaded save game wasn't the problem so i moved 90% of the non-ToI save files to a backup location outside the game directory, and this helped tremendously. 

 

If you are someone who currently has slow load times and a lot of saved games you might want to give this a shot. 

Oh - cool. Never tried that. Removing stuff from your inventory also helps a bit (if it's really stuffed).