Similarly to the 'H7 family, the STM32G4xx also have a somewhat limited lifetime at elevated working temperatures. This fact is documented in AN5738.

This is not surprising, given 'G4 are built in the same 45nm technology than the 'H7, enabling very high integration i.e. (sometimes overly) complex peripherals on a small silicon area, resulting in relatively small unit cost.

Unfortunately, ST does not reveal the underlying mechanism for this limitation. It might be reduced flash retention, diffusion-related issues, electromigration, or any other effect.

While the limitation is not that dramatic as with 'H7 and lifetime even at relatively high temperatures achieves 10 years (contrary to 2 years with 'H7), this is something to be kept in mind when designing with this family.