Is that risky have an unsupported Android version?
My Nexus 5 still working ok, some problems started when apps started to drop support of the Android version, and that happens several years before it stopped receiving OS updates.
Don't want to downplay that will be great that OS updates should be longer that the current standard, but sometimes tech minded people here in HN thinks that a day after stopped receiving updates the phone is a useless brick ais not the case.