How often to test/excercise batteries used in backup system

I have a Victron Multiplus 1000W with two 150Ah batteries in 24v config for standby power for alarm, electric fence. How often should I test and/or excercise the batteries and how long?

Great question I would like to know this as well

There really isn't a "Best" schedule. At work, we cut over to backup once a week for about 30 minutes. A customer I worked with ran off backup power every day for about an hour. I test my generator every month or 2. My batteries/inverter will most likely be run on a similar schedule. It all depends on how mission critical the loads how good you are at fixing problems. For lead systems, it would be probably be good to avoid draining the batteries too much and running up the cycle count. I would run the loads long enough to make sure everything is powered as expected. Maybe do a "calibration run" for an extended period of time to get an idea of what your actual run time will be (being sure to take notes on battery SOC before and after to calculate max run time for the system).