How long should the parent unit's battery last?

Modern closed-circuit monitors advertise 12–30 hours per charge, usually by relying on a VOX (sound-activated) mode that puts the screen to sleep. Verified-purchase reviewers note that real-world battery life with the screen always on is much shorter—often 5–8 hours—so look for VOX or eco modes if you plan to keep the unit on overnight without it being plugged in.