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.