And the only inverters we know will last 30 years had to have been made in the 90s …
Lead acid is much more dangerous than that, IMO, due to the potential offgassing.
This is a common misunderstanding. The lithium batteries used for off-grid and RVs are not the kind you're thinking of. They are LiFePO4, and far less susceptible to thermal runaway than, for example, an average laptop battery.
And the only inverters we know will last 30 years had to have been made in the 90s …