Battery maintenance

I am fairly new to RVing, having purchased my trailer a few months ago now. When we purchased the trailer, our dealer offered a standard 12V lead-acid battery or as an upgrade, two 6V GC2 deep-cycle lead-acid batteries. I went with the upgraded 6V batteries. Now, my question has to do with how frequently do I need to inspect the batteries and check the fluid level. At this point, they are two months old and have been on three camping trips, with two scheduled for next month. I've read all about HOW to perform the maintenance and how to check the fluid level in the batteries but in all the instructions on how to do it, none state how frequently they need to be checked. We are not full-time campers, but we are looking to get away whenever we can. I don't want the process to be so frequent it becomes a pain in the behind, nor do I want it to be so infrequent, I end up damaging the batteries. Is there any advice based on either calendar time or usage time for routine inspection and maintenance?