It usually takes about two weeks to receive an item you request through Interlibrary Borrowing. If the item happens to be readily available in a library with which Stanford has a special resource-sharing arrangement, it may arrive sooner. Some materials may be harder to obtain and may take longer.
If you are eligible to use RLCP (faculty, graduate students, and academic staff only), then borrowing directly from UC Berkeley is the fastest option. If you prefer, you can even visit UC Berkeley (or the other UC campus libraries) and check out materials yourself.