Duplicates [of cables]
are squirreled away in boxes where I can forget about them.
Over the years I've accumulated a huge number of power cords and a
variety of SCSI and serial cables.
Err yes... Mains leads particularly. I have those everywhere. I keep a
couple of spare ones plugged into turned-off sockets on my workbench (UK
mains sockets often have double pole swtiches built in) which I use for
powering up whatever I am working on.
Since I have cats, I buy cat litter in large plastic buckets. These
My cats make use of one of Newton's inventions  and thus I don't need
 THe one that Dr Spooner would probably have called a 'flat cap' :-)
make for great storage of cables once the cat litter
has been used up.
They come with lids that are reusable and they're made from white
plastic so I can write on them with a sharpie to say what's in them.
They have lids that allow them to be stacked and each one has a
swinging handle as well. They work great for storing rarely accessed
stuff like this in a space efficient manner.
How long do they last? My experience with such containers -- ones that
are not supposed to be re=used -- is that the plastic breakds down in a
couple of years. If you have a pile of such contaienrs, it often falls
over at this point, scattering bits everywhere...
I am also concerned about possible reactions between the pasticiser i nthe
PVC insulation and the storage container. Some plastics (expanded
polystyrene -- styrofoam -- is the worst, but it affects others too) will
damage the cable (causing it to go brittle) and also damage themselves.
I've seen what happens if you leave a coiled-up cable on a perspex cover...