I have Spartan cams over my food plots, they work well. I wish they would get better battery life though. I seem to get 1 1/2 months out of them on the 6v with a small solar panel and batteries in the cam. Other than that though. They really seem to be pretty solid.
My BECs use SLA/(AGM) batteries. Most of my cameras are the older 6 volt series. When I get the balance between a solar panel input and programming balanced, they last many, many months before I need to swap them. One of the characteristics of SLA type batteries is that they can take many small discharge/recharge cycles or fewer deep discharge/recharge cycles, but if they are left with a fairly low charge for any period of time, the battery live significantly decreases.
I've had batteries need replaced in less than a year and others last for 3 years and still perform well. I use an Autometer RC-300 to load test them each time I swap them. I wrote some software that reads the receive-logs, extracts nighttime battery levels (the most accurate), and plots the results over time. For a couple years I tracked batteries as they moved from camera to camera through the charger.
My only significant recurring cost is battery replacement. I got a commercial account with Batteries Plus and new SLAs for the Orion run me abut $20 each, but running so many cameras, the cost adds up over time. Fortunately, they replace any battery that doesn't last a year.
I found a solar panel PWM charge controller that will work with 6 or 12 volt batteries. I'm slowly replacing the 15 watt panels I got from BEC years ago with 45 to 60 watt panels and these new charge controllers. With these higher wattage panels, batteries charge much faster. This means that even when we get multiple cloudy days in a row, the panel can usually full charge the battery in a single day of good sun.
Thanks,
Jack