I use nearly the exact setup at home. 2013 13" MBA i7/8gb/512 with a 2010 27" ACD with Apple bluetooth keyboard and trackpad and USB 3 hub. ABSOLUTELY LOVE IT!
Wouldn't trade it for a brand new iMac.
Thank you for your response. What is your habit while using the setup? Do you always use plugged charger or sometimes unplug charging? I just care about the MBA's battery?