I had the experience of buying a large quantity of these batteries at a very good price, less than a euro, from a well-known electronics store that is here and simply does not have all its products on Skroutz. The duration of battery life depends. In others that have a timer with a program, they last longer, consistently for 20 days (without time/program), they last longer than the 30-day ones and less than the timer. That is, they last from one week to three weeks, depending on how you use them. For example, if you use them constantly for 8 hours a day (let's say with the 30-day ones), the batteries weaken in 9-10 days. In general, they have almost half the lifespan of the ones I used to buy.