Many people restoring vintage electronics items are concerned about old electrolytic capacitors. Little is said about vintage ceramic capacitors, but some types of ceramic capacitors age, and can lose a considerable amount of their capacity over time. The interesting thing is that they can be restored by a simple heating process. Check out this web page for more information.
http://www.johansondielectrics.com/technical-notes/general/ceramic-capacitor-aging-made-simple.html