These are a bit lightweight and can tend to crumple/sag under weight if stacked. We use them as single-use containers for lightweight items but I would want a heavier box for long-term storage particularly for heavy items such as documents.
The boxes are easy to assemble. Durable and easy to stack. The only issue I have is the really high cost for 5 or 15 boxes. Meaning I only now purchase them when absolutely necessary. Whereas before when the prices were reasonable I would buy them for portable file holders.