Battery life is highly variable, ranging from one week to one month with minimal occasional use.
The customer service phone number for Greece is out of service. The responses from ezviz via email are standardized and do not help in resolving issues.
Update: After changing internet provider to Cosmote FTTH and placing the router near the entrance door, autonomy has significantly increased. After 1 1/2 months, the battery level is still at 59%.

Good device, nice external design of the doorbell, however, it significantly lacks in capabilities through the application as well as in the display of the screen. Quite expensive for the features it ultimately provides.

Update 22/11/2020: After 1.5 years in my possession, I can say that the application has improved a lot compared to my initial evaluation. I am revising my rating from 3 stars to 4.

Update 31/7/2021: After 2.5 years in my possession, there is a frequent problem when the sensor detects motion in the area. Specifically, the monitor freezes, loses communication with the application, and the battery drains as it remains on until it is fully depleted. You can close it from the main unit button, reopen it, and it unfreezes, but it freezes again on the next motion detection.
The quality/value ratio is very low. With half the money, you can get better systems (see Xiaomi Cateye, Ring Doorview, etc.). The fact that there are stores selling it for 400+ euros surpasses me