long term effects of ultimaker original in idle powered by usb?

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I have got a question about the ultimaker original's arduino powered by usb power only:

I am controlling our ultimaker original with a raspberry pi with OctoPi installed. I am planning to install a wall plug switch to turn off the ultimaker after a print is finished and turn it on again when I want to do the next print. This I want to do with a remote controlled wall plug (the ones with 433Mhz frequency conrol).

But then there is the fact, that if I switch off the ultimaker main power supply (either by turning the power switch or cutting power with my planned remote control), the arduino, the blue print head LEDs and the conrol shield display still get powered by usb. I use a powered USB hub, so the power gets not drawn from the raspberry itself.

My question is, whether it is still not a good Idea to let the ultimaker (without printing) run with usb power for longer times? Because sometimes the display dims a bit or has other strange behavior. Maybe the arduino gets too hot down there under the ultimaker without the fan running? Is there anything that can be caused by usb power not sufficient to supply enough power (for example for the display)? Any long term effect that could appear?