Well, until the batteries go flat, or they are dropped into the foot-well
Er, that's not how they are used in microlights and other permit aircraft. Usually the "handheld" is mounted on the panel and fed from the aircraft's power supply. £200 instead of £1000 for a panel mount (rough prices).
And the issue has been that when they are on a fixed mount and plumbed into the supply they have to be declared on the aircraft's radio licence - so they need approval.