Direct answer
Paper per-item despawn times affect how long specified dropped item types remain on the ground; this is not a setting for inventory contents or hopper transfer.
How to check it
- Confirm the item ID you want to target and measure dropped-item counts while that item is accumulating. Use a controlled cobblestone drop test with an unloaded and a loaded area; identify whether the cost really comes from dropped items rather than containers.
- Record the original configuration or test conditions, capture a profile or a repeatable observation, and identify the affected world or player group.
- Make the measurement under the same player count and workload you will later use to verify the change.
What to change
In Paper per-world configuration, spawning.alt-item-despawn-rate.enabled must be enabled before entries in its items mapping apply. Values are ticks, so 300 ticks is approximately 15 seconds at 20 TPS. Keep rare drops at sensible lifetimes instead of shortening every item indiscriminately.
Players may lose items before collecting them. Check both collection time and entity count after the change.
Software and version notes
Check the active version and generated configuration before copying paths or values. Different forks and mod loaders may implement this behavior differently.
This article is written for Paper / compatible servers. Configuration keys and defaults can move between versions. The source material checked for this page includes Paper world configuration. If your server is Folia, Leaf, Purpur, Fabric, Forge, NeoForge, or another fork/loader, do not assume a Paper-only setting exists or behaves identically.
Verify the result
Repeat the same test with the same software build, player count and world activity. Compare the targeted symptom and any spark measurements, then check that intended game mechanics still work. If the change does not produce a reproducible improvement, revert to the recorded baseline.