My old trusty13" MBA is late 2010, 1.86 GHz Intel Core 2 Duo, 4GB memory, 256 GB SSD, currently running nicely under OS X El Capitan 10.11.6. Should I update to mac OS Sierra? Will this machine run well under Sierra? And under the upcoming macOS High Sierra? My main computer is a late 2014 retina iMac, so the MBA is now used only for occasional trips and for part-time use in the house when I am not in my office. In the near future, this MBA will become my wife's main computer, replacing an old mid-2009 24" iMac.