I would think trying to reuse it would end up with it being diluted somewhat. Even in my 24' trailer I am getting rid of, I only use one gallon every
fall. The stuff is quite cheap. The RV antifreeze is fine to treat just like gray water, it can be dumped or spread onto the gravel. I just usually release mine into the trees at our rec property with no problems at all.
NEVER use regular anti-freeze, the type that you use in radiators. It is highly poisonous and can kill you if ingested.