If they are from SE prints, it's doubtful much fading would be evident. Willitts Designs sold 70mm cels from all 3 OT films from pre-SE prints in the mid-90's and so far only the ROTJ prints show significant signs of fading (different stock used).

True dye-transfer prints did not use a photochemical process so there was no Technicolor "stock" per se. They used blank/clear strips of "film" for their printing (which was a lithography-type process).

On a side note, I don't think any true IB Print would say "Eastman Safety" because that denotes a photochemical stock.

http://www.widescreenmuseum.com/oldcolor/technicolor1.htm

It's interesting, though, and definitely worth a bit more research. It's too bad that the cels are 'scope.