I've seen the Red Oak heartwood still out there after the sapwood is long gone....the heart will last 20 years or more if it's off the ground.even some of the rotten looking stuff that has fallen is still good firewood. I had a small red oak fall a couple of weeks back....I was amazed, when I took the saw to the log, to find that the heartwood was still rock solid - not rot, not insect damage. I thought the log migh break apart by hand it was so rotten looking. Most of the bark was long gone....The sapwood was all punky but there was only a thin stripe of that so I hacked it off the rounds, along with any remaining PI hairs and ended up with 21 good rounds of red oak heartwood to split.