How can I put this..
Does old skins shrink?

The reason I'm asking is to learn more about how skins are treated and how they're size will differ from the "original".

I hunted Namibia in 2004, and my trophies came home as dip and pack.
I've displayed the horns of an oryx, hartebeest and kudu Euro style and kept the skins in "sealed" plastic bags in my freezer.
A while back I decided to have them mounted. I will have them all three mounted on a single, big pedestal.

The skins have now been in my freezer for over 5 years. I sent them to a tannery and my taxidermist have started receiving them. The first ones looked good he said.

And now comes my question. Does skins normally shrink after these years? In the freezer? Will the tanning or taxidermy work stretch them back to "normal" size? How does this work?
Do this have anything to do with quality of tanning/taxidermy work?

Thanks in advance!