The thing to remember is that its going to be shared memory, and most IGP's memory access can be limited in quantity. That being said, the IGP doesn't care a bit when you are loading a large spreadsheet or what-not. This requires no shaders and generally won't even have a measurable impact on your CPU. If you are worried about it, set your IGP memory down to 128 MB.
Sony Zeiss 55/1.8 SSM, 24-70/4 SSM
Minolta 17-35/2.8-4 D, 35-105/3.5-4.5, 100-300 APO