How do you stop the wood from rotting? Mine are all rotting away. I found
a
crisp packet with a 2001 "best before" date embedded in the concrete of
one

You're supposed to soak the end in preserver overnight. Personally, I just
use concreted in Metposts. Also, concrete is supposed to be installed clean.
Embedded crisp packets don't bode well for strength.

Christian.