Performance changes to metal can transistors installed 40 years ago
These are hermetically sealed cans, so they're not much subject to environmental attack. Migration of the dopants over time can change the geometry of the layers, aging germanium transistors would sometimes improve in gain and frequency response with aging as the base layer thinned. That, plus migration of the metallization for the electrode attachments are the main worries, but these are fairly physically big dies, and if they'be been stored at a reasonable ambient, the change will be minimal.

MIL-HDBK-217 prediction of failure rates probably don't mean much at the extremes of projection of life and failure rates, but all the factors lead to the obvious conclusion - the transistors should be fine. It's the carbon resistor's I'd be more worried about. Film resistors would be better for extreme durability, but if the design is tolerant of some drift in values, it may not matter.