I have an old big bin of at least 20,000 Lego and Lego-like pieces. I never kept the boxes or the instructions when I was finished building sets and I have Lego pieces from at least 50 different sets, plus other non-Lego brand bricks of various types. I could sort it out, but that would take an extraordinarily long time. I want to know if they have any play value left; if I can still use them as Lego without any instructions or boxes, and no memory of what half of the sets that went into it were. Do these pieces have any play value, since they are random pieces with no way to reassemble the original sets?
It definitely has a lot of play value for random creative building. With a box like that I would recommend to donate it to a primary school or kindergarden. If they have lego it would be in exactly that form anyway. A nicely ordered collection of indivual boxes with manuals would just quickly be turned into a huge mixed box anyway.