According to Matthew Reed nospam at zootal dot com nospam:


It has always seemed to me that those metal post holders that you set in
concrete would be a better bet. The end of the post will be able to breath
some, so it should last way longer. Plus, replacement would be way easier.

Bob

I'm not sure I've seen these before, but I think I know what you are talking
apart. Do they hold the post securely enough to take the load of wood,
gates, etc. ?

No. They need side support if they're of any height or significant
side load. Same for "post spikes". Not suitable for fences or
freestanding decks (unless very short).

The trick with concreted fence posts is to bed the bottom end
of the post in several inches of gravel before pouring concrete.
Any moisture entering the post can leave out the bottom, and the
bottom isn't held in direct contact with moisture. PT posts
will last a very long time when done properly.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.