I know that cleaning is taboo, but... but... but...
It seems so wrong to encapsulate a coin that has not at least been rinsed of accumulated dust, debris, skin oils, etc-- stuff which could potentially adversely affect the coin over time.
I'm sending some coins off for slabbing soon and am worried about this, perhaps unreasonably. Do you clean (correction, 'conserve') your coins in any way prior to sending off for slabbing? Maybe a quick acetone rinse?
On a related note, I've come across a large number of coins which were stored in vinyl 2x2s. Ugh. Bright teal-green polymerized gunk, requires several long acetone soaks to remove and the coin's luster is affected underneath the residue. Bummer.