Are Mojave Express Dropbox's effectively storeage.
Sorta. You can use them to ship an unlimited number of items to any other dropbox. However, you can't retrieve items from the dropbox you put them in, as far as I'm aware.
I'm getting to the point where i can't carry everything I want to keep and I don't have housing yet so I was wondering if you can indefinitely keep things in the Mojave Express Dropbox's because i haven't found any other use for them yet.
I haven't tested it, but theoretically, this would work so long as you didn't actually use whatever dropbox you shipped the items to until you want them.
I'd test it if I were you though, because it might be that one shipment could "overwrite" another, leading to the first shipment being lost.
Like if you ship two guns to goodsprings from Primm, the second shipment might overwrite the first one, leaving you with only one gun. Or perhaps not, I don't know. Like I said, I haven't tested it or looked at it in the GECK.