as long as

1. During the time that: I'll stay as long as you need me.
2. Since: As long as you've offered, I accept.
3. On the condition that: I will cooperate as long as I am notified on time.

1.  For the period of time that, as in You may keep the book as long as you want, that is, keep it for whatever time you wish to. [Early 1400s]
2.  Also, so long as. Since, because, as in Please pick up some milk as long as you are going to the store, or So long as you're here, you might as well stay for dinner.
3.  Also, so long as; just so. Provided that, as in As long as you don't expect it by tomorrow, I'll make the drawing, or So long as sales are greater than returns, the company will make a profit, or You may have another cookie, just so you don't take the last one. [Early 1800s]