I was playing a 5 star, 50 planet game of entrenchment. I was running with all the graphics options up as well as a volumetric explosions mod to improve the graphics of the weapons and explosions. If I load my saved game, it hits the limit in about an hour. Task manager reports the game process at 1.8gb of ram.
Truth be told, why have the high-res options, if there is a limitation imposed by the 32-bit application? Or, why not make two versions of the executable for 32 and 64 bit. Other games I've played have done that, probably to avoid hitting this issue.