So I'm suppose to get out there and just wing it? lol. I'd like to at least have an idea of what I'm dealing with prior to a trip
Well, yes... That's how we all figured it out... How do we know what your potty and other water usage habits are? ;)
I know you don't know the size of your tanks, but they should be around 30 gallons at least each and then you just have to know how long you can go with your water usage you can go before dumping. No other way around it..
Some can go for a week or more. Some can't even go a day..
You probably fall someplace in between?
Good luck!