GriefPrevention - How To Protect/Claim Land:
NeORollBack - This plugin will automatically rollback any changes you make in all worlds (for example, every block you placed or broken) if you do not join the server at least once within a 30day period.
This means that if you join on the 15th of January and do not join back until the 20th of Feburary then anything you have done in any of the worlds will be undone. This CAN be restored if owner requests via a Head Admin.
It does not matter who owns the claim placed around the blocks nor does it matter who started adding blocks/changes to a house for example, all that matters is if "BoB" placed a block and goes inactive for 30days, that block will be removed even if
"Paul" placed a claim over that block or started building around it.