I don't know if I can speak here for most, but I would say:
Turn it off at night, if that pleases you - it's your choice.
If you bought that new iMac with an SSD, boot is really fast, maybe slower if you have a fusion drive.
Or, leave your iMac on, and simply sleep your iMac when you are not using it.
I think that many here do not shut a Mac off at night. I think the last time I shut my Mac off overnight was about 6 months ago. It is almost never off.
Put your Mac to sleep. That's a very low power mode, virtually no power used at all when sleeping.
Then, press any key to wake up, often almost instant wake, certainly less than 5 seconds.