I think it’s a good idea to unplug all unnecessary, high priced electronics. This will eliminate the risk of damage from a power grid fault or nearby lightning strike.

But it’s also OK, as Sonos equipment automatically goes into low power mode after a few minutes of non-use. 

We leave our Sonos speakers on when away from the Home, as they play a small role in our Home security when in sleep mode, as both motion detectors (HomePass Sense) and also for sounding an intruder alarm (Hue Sensors/Lights & Alexa Routines).

A week, probably not.

A month and I’ll power down a lot of stuff on top of the Sonos.

I agree; I do this even for a week. Everything except the fridges perhaps. Reducing power bills is bottom of the list of reasons for doing so.

Think green… everything big starts with the small things. I remove my devices including Sonos from power, if I don’t use them for about 5 days. The ones I rarely use are unplugged by standard and I just turn them on when using them. E. g. my rearspeakers or the one in the guest room. 

Don’t bother. It’s all plugged in when you are there, makes no difference if you are not there.