I haven't found this mentioned or explained on the wiki or forums, so I came here.
I farmed a huge amount of trees (~300) throughout the winter. I couldn't be bothered to collect it all, so I just left it on the ground. As spring started, I went away to farm bunny puffs because I wanted to take advantage of the long dusks. I come back a few days after the summer starts, and all the wood and pinecones are gone!
Somewhat luckily, I had set my rollback length to 15 snapshots, and going back, it's fairly apparent the wood disappears gradually, similar to how I cut down the trees during winter.
Is there any info on this? I assume the game performs maintenance to keep the item count reasonable, but deleting stuff after just 20 days.. I dunno. Would have hoped it would stack it like teeth and monster meat from hounds are stacked.