Fiwit: great beds! They look really good. And I bet landscape timbers last a long time in contact with soil. How thick are they? I guess less than 4".
They might stay drier and last longer if you line the insides of the bed walls with heavy plastic film below soil level. For example, the bags that the soil came in. That may be worth doing if you find that the edges and corners dry out faster than you like.
i love the policy of "holds yard waste this year, hugelculture foundation the next few years, soil after that". If you ever let a bed lie fallow, for example to deplete the weed seed bank in the soil by growing a few biomass cover crops, you could harvest the top growth to give a new bed a head start.
Thanks very much for the tutorial! The photos make it a very easy read, and you've got me thinking about pricing landscape timbers.