Shep,
In the SSWS run (including a 144), I have 5 slabbed books so far. For storage and protection, I have left all of them in the slabs. I will probably break them out at some point and save the labels as you have done. My Oakland SSWS books look fine in mylar and the others would too.
I have been wondering lately if CGC will ever put up a SSWS 151 on up Registry set (or Bronze OAAW/Rock, GIC, OFF, or US - for that matter). Even though I am not into the Registry thing, that may prompt me to start slabbing my high grade/pedigree copies in the run. SSWS would probably be the only title I would do that with.