Here’s a tip for the day: When your lenses aren’t in use, or whenever you’re traveling with them and they aren’t actually mounted on your camera in their normal way, always reverse mount the lens hood, like I’ve done here:
Reverse mounting the hood aids in the protection of the lens barrel. And, since the lens is now shorter than it otherwise would be with the hood mounted normally, it takes up less space in your backpack or luggage.
I firmly believe that reverse mounting the hood, along with having a protective filter on the front of the lens at all times, will significantly decrease the exposure of your lens to any sort of drop or bump which can dent or scratch the lens barrel or front element.
Also, if you want to do any shooting without your lens hood mounted in its normal fashion, and you aren’t doing any manual focusing, I’d keep the hood on reversed even while shooting. If you’re as clumsy as I am, at some point in the future you will drop a lens. And when it happens, I’m always thankful for having that lens hood there for extra protection.