Yes. You can reuse a full box as many times as you want. If you don't need the originals of the documents in your box anymore, you can begin by emptying the box and destroying the documents. Don't worry, all of your copies can still be found in digital form in your fileee account!
Then you take a new QR code sticker (multiple stickers are included in the delivery) and stick it over the old one on your fileeeBox. Now you simply have to link the box with the new QR code to your account, and then you can start filling your box anew.