The RoW sound system from 1990 used a single memory for each sound. The memories were guaranteed to hold their data for 10 years. Interestingly my sound systems still work 30 years later. It has a lot to do with the many variables mentioned in the above [GRJ] post.
One of the additional factors is the initiation of RoHS (Reduction of Hazardous Substances) standards. This demands the use of lead free solder. Tin solder has the odd ability to grow tin whiskers,(https://en.wikipedia.org/wiki/Whisker_(metallurgy), thus shorting out otherwise operational boards. I spend a lot of time in my introductory MEMS (Micro Electro Mechanical Systems) class explaining RoHS and teaching methods to work with lead free solder.