I have the mid-2011 MBA, I see signs of problems begin to come one-by-one. Problem: 1. Youtube freeze while watching, sound still plays. 2. Battery service alert on. (230 cycles, 79% health) 3. beach ball spinning while 15 Firefox tabs opened, can't switch between screens. My answer + advice: 1) I really think running loop damages your MBA. I brought this up in here two months ago. I was writing 700,000,000 for loops, and it takes 1.5 days to complete the job, don't ask why. (http://forums.macrumors.com/showthread.php?t=1535723). 2) Cold weather shortens battery life. Before the winter (4 months ago), battery was 90% health. I walked the MBA through snow, from parking lot to building, alert was on, no big deal, but battery life began to shorten noticeably.