I have a MacBook Air which is the 2012 model. Now I will charge it up and switch it off so that if I need to rush off somewhere I have a charged laptop with me. When I say switch it off, I do mean switch it off properly. Shut it down. I sometimes won't use my MacBook for 1 or 2 weeks. However, when I do turn it on again, I either find that the battery is either down to 50% or almost to 20% - it just depends for how long I have not used it. Is this normal? I always thought that the charge would at least keep for several weeks, if not a month or two! Thanks.