It's quite a colloquial context so hard to say clearly but it doesn't mean 'just before'
'just as long as' is often used to say 'it doesn't matter, if something else happens'
Child - "Can I go out tonight?"
Mum - "Just as long as you're back by nine"
In this case it sounds like B is saying, I don't mind when or if we pay the debt as long as we get back to the North for summer.