While Dave is correct about valuing strips, you are right as well. Older strips (between 1981 and 1986) do sometimes have a premium value for the strips that are rare or hard to find. I know of only one dealer who stocks and sells used strips, but I don't know what the demand is for those longer strips. If nothing else, you can list them on eBay
yourself at the price you want and see what happens.
I don't know of an English term to describe "really used", but I've seen descriptions of covers created for stamp collectors/dealers called "philatelic covers".
Like Dave, I'm interested in singles you may have to trade especially the 32¢ Flag Over Porch issue as I'm building an exhibit around that stamp.