I'm getting a mid-2012 MBA and plan on always keeping an external 1TB USB 3.0 HDD plugged in at my desk (USB Powered). Could this cause overheating or other issues? Anyone out there run an ext. HDD full time with a MBA? Since I got the base 128GB SSD, I will be using the ext. HDD for large downloads, work files, etc. Just checking if this is a bad idea or not.