You will love your new toy
I can't tell you how long the battery will last, I have never used mine until it was flat
I can get two 3 bedroom houses on a full tank on setting 2
If its a first clean I use setting 2 if its a regular I can turn it down to setting 1, I have never used setting 3 and 4.
I use a 12v caravan pump to fill mine up takes less than 2 minutes to fill, I used to use my 100psi pump on my trailer but I could have a cupa tea while waiting for it to fill up.
I don't carry it on my back, I put it onto a folding trolley make life a lot easier.