IMHO, there is no (affordable) subsitute for ALWAYS having a very small and very quiet generator along in your RV for battery charging. Perhaps fuel cells will eventually be affordabe enough to replace a small generator for this purpose, however.
Solar is of course another redundancy capability that's great to have aboard your RV for battery topping up when in storage and when drycamping for long periods in the same spot. With weather now going the direction it's going everywhere, it seems risky to have only the sun to count on for drycamping battery maintenance.
We have been RV'ing for around 45 years and have never needed solar. However, we don't full-time camp in the same sunny spot for months on end, we have always used a self-contained RV with at least it's engine alternator for emergency battery charging, and we have always been able to store our RV close to a shore power outlet. We may soon add a small, foldable, portable solar array into our mix for improved RV drycamping choices.