I have 13 inch 2013 model..and plan to sue it for a long time ahead.. But its 256 GB. Although I dont need much more, I saw today I can buy 128GB SD cards for just $60 or something... If I plug them in ALL THE TIME..meaning just like default macbook storage, will it affect overall battery life? I guess yes, and I think it might affect in a big way...whats your take?