They are not affected quite as drastically as an acoustic piano because they don’t have a soundboard. You may experience some notes drifting a little, but that can’t be avoided. Every CP-70 owner should learn the basics of piano tuning and get a tool and a couple of mutes. Tuning the entire piano is a whole other issue, but touching up a few notes is not that hard. You just have to be very sure you are tuning the string you want to tune and not one next to it to cut down on accidental string breakage. You especially don’t want to break a bass string.
Note to all CP-70 users, if you ever break a bass string, do not throw the string out. A piano tuner may be able to splice it. If not, they NEED the old string to send to a factory to duplicate it.
Also, avoid touching copper strings with your bare hands. Perspiration and skin oil can ruin the tone.