The Ring 3 is treated like a battery device, irrespective of it being wired in. This is the same as the stick up cam gen3.
I wrote to Jeff Bezos and had someone from Ring contact me about recording lengths and these issues with the powered devices.
They confirmed there is no plan over the next 12months to increase or provide options to increase length beyond 30secs for battery powered devices even they are powered.
Was left pretty soeechless, I mean at least it was a definite answer rather than we are passing the feedback on!