They should have kept the phones
Can ANYBODY show me an Android phone sold in 2016 that gets updates until 2019? Anyone? Beuller? The windows phone was a SMART purchase if they wanted phones that would get security updates for the long haul, instead they'll end up with phones that they'll need to toss every other year if they are lucky.
And before anybody brings up apple, have you ever used an older Apple phone with the latest OS? Talk about painful! Say what you want about MSFT about windows 10 actually made 8.1 phones snappier and more responsive, not less. I've never sen an Apple phone that ran faster after being updated to the latest and greatest from a previous version, this is why my apple customers simply replace the phone when the new Apple phones are released, not really any point in updating those if you want a snappy and responsive phone.