Always a good idea to have more 12 volt reserves when camping off the power grid, if you have the room and don't mind the extra weight go for it. Your current GR24s are not ideal for this type of use and you will experience better results just by purchasing golfcart batteries which lend better to this style of RVing.
We have an onboard genny and a portable inverter genny, no matter either are going to be used on a daily basis. Most often it is for powering high amperage devices momentarily. When our solar can't keep up due to weather of heavier than normal 12 volt depletion, genny is utilized along with our Iota to quickly restore consumed amphours.
Our 12 volt reserves consists of a pair of 6 volt GC2 batteries from Samsclub and they suit us fine. We don't attempt any drastic measures to reduce 12 volt power consumption, we use our rig and it's amenities as we deem necessary. We did do an LED conversion a few years back effectively curtailing daily 12 volt consumption.
This method of RVing is easily our preferred camping style, nothing is of greater importance for us than being 100 percent self-reliant and self contained. We often camp in extreme temps whether planned or due to quickly changing weather patterns, being able to use our rig to it's fullest capabilities is paramount under such conditions. Sure, we could cram another pair of batteries somewhere but what we have works just fine.