Storing Mounted Prints

I'm rapidly building a collection of prints entered in club competitions mostly in 20"x16" mounts. Problem is arising of how to store them. I have a suitable size box but I don't know the best way to store them INSIDE the box. They are a mixture of colour and black & white.
Should there be a sheet of paper between each print?
Should they all be stored the same way up or print side to print side and mounted side to mounted side?
Any advice much appreciated.

I wouldn't store them print to print, especially if they are inkjet prints. Any damp and they could smudge from print to print.

We just store ours vertically in boxes, open to the air. They have lasted OK up to now, although how long for an inkjet is something else.

Thanks John
I've just found that I can buy 500 large sheets of acid free tissue paper for about a fiver. Think I might get some and shove a sheet between each print.

This is what I use, link, a fantastic company to deal with too

Thanks Ken. I already have a Nomad box. I too recommend them.