Which is interesting, as the shipping companies are very, very adamant about getting their empty containers back before your 'free time' runs out. I got one email return reminder for a container that hadn't even cleared customs yet!
Every time I get a container, I have to pay for a container bond, and don't get that money back until I send them the EIR, and pay for any overage for extra days out.
And yes, a lot of the containers used for construction are past being able to be certified for international shipping. I can get non-shippable containers all day, but the certified ones are kind of scarce at the moment.