currently almost all materials over this time frame will suffer from differences in CTE or coefficient of expansion, e.g. there is a minute difference between the pins of a microcontroller and the package of one, its small, but its there, this will also be different to the FR4 pcb material and different again to the SMD passive packaging,
In general these will be close, but over 80 years, things will slowly tear off there joints unless you get very specialized, to clarify, BGA and QFN / DFN are out, and cannot be used, even for passives, throughole may prove better so long as you follow correct lead forming,
As for weatherproofing, you say durable, but fail to give an indication of to what extent, for this time frame I would be thinking sealed in glass with external connections welded to the pins, and have desiccant packets inside to reduce the very slow long term leakage the seals will face. the glass blower can use UV repelling glass, however I do not believe the coatings are expected to last beyond 20 years in direct exposure to sunlight.