I know there are several types of capacitors, in terms of the materials used to make them. Are some types more stable than others? Are some types not a problem at all, regarding time, disuse, heat, etc (i.e. they are very stable over many decades)? I am asking because I will be ressurrecting a late 1970's Quatre preamp, and the friend who will be putting it together for me says that some of the caps will be good and stable despite no use for several decades (depending on the type of cap).