I've had my 13" early 2014 Air (4gb/128gb) for one week. The battery is on 100%, but says I have 8.55 remaining (no external drives plugged in). The blackmagic speed test gives results: 205 read / 450 write. I upgraded to Yosemite, before which the battery life seemed normal. Software loaded; Office Onedrive VLC Acrobat Pro trial Unrar Is it worth doing a clean install or might there be a more serious problem?