Shipping product ain't like dusting crops, kid. One wrong move and you end up as dust on the sea floor.

Also blimps won't come back because we're running out of helium on earth. (But there's so much on not earth!)

I don't know about XCOM, but wave 6 has been on the boat for maybe a month. It takes about 6 weeks normally for stuff to get from the printer to FFG and another week or so after that to get to the stores.