Rob, if you have had good luck, great. I have finished some cedar without a problem, but my response was an alert based on advice I have consistently seen on various forums... for example...
From Jeff Jewitt's finishing forum, talking about finish for a blanket chest: "Blanket chests are typically not finished on the inside, partiularly if any aromatic red cedar is used. That includes the underside of the top and the tops of the sides. The chemical responsible for the pungent smell of aromatic cedar is cedrol, a chemical related to camphor compounds. This gas will soften a finish used on the inside. If red cedar is not used, you can use any evaporative finish you like, including shellac and lacquers. Don't use any oils or oil based products, even water ones like the Fuhr 255 (on the inside).
From the Fine Woodworking Knots forum, numerous discussions including this techie answer about finish being softened ..."I have heard of this happening with lacquer before, but I didn't know it could happen with Watco. Aromatic cedar has a few chemicals that can cause a finish to plasticize. Limonene and bornyl acetate are two that are present only in freshly cut cedar. So if you can remove the tray or leave the lid open for a week or so these will dissipate.
"If you still have the problem it is most likely caused by 2-hydroxycamphene which is the chemical that gives cedar its smell. You can't and don't want to get rid of that without waiting years. Depending on what finish you are looking for you could use an alkyd-resin varnish, shellac or a waterborne acrylic to finish your tray. If you don't want to strip the existing finish I would try making a sample that is finished the same way as the tray was and seal that finish with shellac. Put your sample piece in the same conditions that caused the tray to plasticize and see what happens. I will bet that good old shellac will rescue another woodworker from a sticky [pun intended ;-)] situation.
I don't want to start a war, especially since (like you) I have finished cedar without a problem. However, I have also seen numerous warnings, like the two above, that make me worry about finishing anything in a confined space with aromatic cedar. Other discussions have ruled out other finishes until I was left thinking that Shellac was the best choice... maybe the only choice