I had three of them and never noticed, but then I did not run them mobile very much.
I suspect that the parasitic loads from the car itself are in the same order of magnitude.
I think that the radio just keeps the low power mode on the CPU alive so that pressing the power button is recognized by the radio and pulls in the power relay.
If you are to be gone for a long time you could just pull the + side fuse to kill the load. That would keep the contacts clean as well.
Adding a switch is probably more work than I would do and adds another point of failure.
I sold all of my IC7000s and bought an IC7300. That radio is great, but I miss my colorful 7000 and its HF,VHF and UHF.
I bought a FT857 (dead) and resurrected it for the combo, but it is not a 7000.
Good luck and best regards,