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]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use as long as in a sentence