I am sure you are right Chris. A lot depends on how hard I push the batteries I think. While it would be nice to have a system that I could push hard, I know it isn't the case
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I have 7AH power tank for the scope. Most nights it only takes a very short while to recharge (usually only minutes) unless I've been GOTOing like a madman or have used the 12V hairdryer or something else on it as well. So if I just use the scope, I'm confident it's OK for 3-4 nights.
I have a 24AH jump starter pack that I've been using for the dew heaters and laptop. Obviously with the lappy, it sometimes cops a caning, so I have just recently also bought a 38AH jump starter pack as well.
The dew heaters draw <2A max. and I have a PWM controller on it so I can (hopefully) manage that as efficiently as conditions allow. Obviously I can't expect to run the dew heaters all night and have the batteries fully recharged the next day...
While I know it's not ideal, I'm hoping I can manage things so I've got reasonable power for 3-4 nights without having to fight for power at the house. I just have to be a judicious about when and how much I use the laptop I think. It's the thirstiest power user.
A little more observing and perhaps being a little more discerning about imaging may be the order of the camp for me.
I don't expect to come home with fully charged batteries though!
Al.