Your trucks are probably aluminum and will be fine, and you can run sealed bearings. Riding in the wet really isn't such a big deal. The biggest problem is spray off of the wheels.

The board damage (if made of wood) is unavoidable though.

You can seal the wood with some kind of lacquer, though, right?

This is too bad, because I live in Bergen, Norway, where according to statistics 65% of all days have rain. So I'd have to resort to walking two thirds of the year => No longboard for me, electric or otherwise.