I just replaced the stock touchscreen head unit in my 2013 Camry LE with a Kenwood DMX-8709S and Maestro RR module to retain steering wheel controls and car settings that were set through the original head unit.

There is a Maestro setting "Accessory During Crank" that I am really tempted to turn on. It keeps the head unit on from the moment you turn the key from lock until the engine starts. Otherwise, it would turn on as you go to accessory and then reboot again as you go from accessory to start and then to run position.

According to IDataLink support:
"This feature simply keeps our relay latched when the car is cranking, so that the red accessory wire that powers radio stays on."

And it does not affect anything other than the head unit. When I asked if other accessories are affected, the reply was
"Our relay does not have a way to backfeed itself into the vehicle or change the way the vehicle operates "

Is there any reason NOT to turn this on? Any unintended consequences?
Could this damage the new head unit in any way, or the car electronics? Or the battery?
I'm thinking not but want to hear from others. Especially others who use this feature and can report from personal experience.

 

Might check at the Toyotanation.com website which as a in depth entertainment system forum.

Don't know but the stock radio, clock, computer already have a dedicated hot wire to keep pre-selects and correct time,