I think it depends very much on the climate where the device is. Damp is a serious enemy to electronics.
Device in an unheated and damp area - I'd never switch it off. Its own heat will provide some protection. I've tried silica gel, but it's more faff and doesn't seem to do the job for me. Also, SWMBO didn't like be putting strange things in her oven. She puts up with many of my other strange habits.
PC at home gets restarted once a week, but does all its "stuff" while I'm asleep. The monitor turns off after a while but the rest stays on.
The TV set gets turned off, but the PVR stays on - it hibernates itself as required, and wakes itself back up when needed. I've just changed all the capacitors in the power supply because the heat (when running) had cooked them. There's a fan in there now, and higher-temperature rated Cs.