The reason for the wood in the bottom is to store moisture, not to produce nutrients for the plants. So you should prefer already weakened/semi decomposed wood

The reason for the wood in the bottom is to store moisture, not to produce nutrients for the plants. So you should prefer already weakened/semi decomposed wood (just pick old tree branches off the ground in a forest). Besides, as the linked article explains, a typical mound has a lifespan of 5-6 years [1]. I don't see how your argument about human lifespan is relevant here? 1: https://en.wikipedia.org/wiki/H%C3%BCgelkultur#Lifespan https://en.wikipedia.org/wiki/H%C3%BCgelkultur#Lifespan