"George" wrote

I'm doing some structural work on an old addition. A fair amount of the
wood I take off is in decent shape. (No water damage, in particular.)
It's T&G sheathing, 2x6's, and (especially) clapboards. It all seems to
nail OK.

It would be nice to just re-use this stuff, where I can. Is there an
informed opinion on doing this?

I take it you are putting it back up where it came from, replacing a few
pieces as needed? It will work fine if not warped or damaged (as you seem
to indicate).

You may find a few pieces break or are otherwise damaged when you take them
down but likely as not, even those can be re-worked for trims or smaller
spots. A bit of a pain cleaning it up, but not too bad. I find it about
even to the pain of having to make a trip to the local dump to get rid of
it.