Door Bell battery does not last

We have a Standard Door bell which is on battery. Initially the battery was lasting around 3 months but was picking a lot of foot and vehicular traffic. We have changed the range and only to pick up foot traffic but in saying that we now only get around 4 to 6 weeks battery life. This is a real pain....we were expecting around 12 months or at;least 6 months. Does not really help if you decide to take a 2 month holiday, the door bell becomes useless. How long are your units lasting before needing to charge it up again..... I know there is now a solar units we can buy but it notes to be in some direct sunlight. Our unit is located under a Porch and I believe it would not receive much sun at all. Will this unit charge with very minimal to zero direct sunlight. Still dissapointing that we now have to spend more money on a door bell that costs us a bit to start with and pay for a video service each year.