I mainly shoot 6x7 and keep them in sleeve pages. Sometimes I'm too lazy too put them in there and will just keep them in the sleeve that comes from the lab, these is usually if I don't think I'll do anything with the neg. I've been keeping them in old 11x14 paper boxes with the contact sheets, the boxes are labeled with the year/project.
This is a shitty way to organize, don't store yours this way. The best way I've seen is in a binder that closes on all sides with the contact sheet in a sleeve holder and the negs in a sleeve page behind it, very easy to flip through.
edit:
@Matze- Printfile sleeves (that's what I think you have in the pic) are acid-free so it should be archival for the long-term.