fromEnglish Grammar Today
As long asandso long asare conjunctions.
As long as
We useas long asto refer to the intended duration of a plan or idea, most commonly referring to the future. We always use the present simple to refer to the future afteras long as:
We are very happy for you to stay at our houseas long asyou like.
I’ll remember that filmas long asI live.
Not: …as long as I will live.
As long asandso long as
As long asorso long asalso means ‘provided that’, ‘providing that’ or ‘on condition that’:
You are allowed to goas long asyou let us know when you arrive.
So long asis a little more informal:
You can borrow the carso long asyou don’t drive too fast.