40+ end turn duration

[Idolize]

Hey, I'm new to this forum and I was hoping I could get some advise on why the loading times in between turns take so long. I am on turn 350 on a modded "earth" map, with max civilizations and city states. When the game doesn't crash, and return me to windows I am stuck waiting around 60 sec until I can finally get back to the game. My comp specs are fairly decent:
AMD athlon X4 2.9ghz
ATI Radeon HD 5770 DDR5
4g ram DDR3
Windows 7 ultimate 64bit
I run at max settings with a low resolution of 1280x1024(17' monitor)
Any help would be greatly appreciated.
Thanks.