Ars Technica:
There are still good reasons to want an old, reliable USB stick. For instance, if you find yourself doing multiple installs, a USB drive may be faster than multiple downloads (especially if you use a USB 3.0 drive). Or maybe you need a recovery disk for older Macs that don’t support the Internet Recovery feature. Whatever the reason, you’re in luck, because it’s not hard to make one.
I always prefer to have at least one “offline” copy of the latest OS X version.
Sage advice.
I’ve always had difficulty with using the “offline” installer when necessary. It still wants to download components from Apple, and it ends up just downloading everything as if I opted to install via the Mac App Store. That’s how I’m having to install Yosemite on my beta partition drive from my IT guy’s bootable install drive. Shouldn’t the USB stick bypass that entirely? Am I doing something wrong here?