The thing about RV battery banks, is that they are likely to be built in, under a bench etc. Getting access to them every 6-12 months to check on the balancing would be a PITA. Initially, i had thought that an active balancer would distribute up to 6A to each individual cell, all the way up and all the way down, thus no further possible problems with unbalanced cells. Thats not how they work....shocker. My understanding is now, that they mainly do their 'work' in the 'knees', where the detectable voltage difference becomes apparent, however, they struggle to keep up, with the rate of change. With passive balancers, they bleed off energy from the single highest cell once in the knees. So all the talk about cycling battery banks between 75% - 25% SOC to achieve many more cycles, is in reality, just tosh and cant be accomplished in a practical sense by the average DIY'er. So is charging well below the ceiling at say 3.4v/cell or below, trying to stay below the 90% SOC. You need to reach the higher voltage to activate the ions and trigger the passive balancing once in the knees.
Now, may well be, by much anecdotal evidence from members, that the amount of cell 'drift' is so minimal, as to be pointless worring about, but nevertheless, they all want to keep checking on them....i'd say that was a niggle.....lol.
