Losing improvements

Once an improvement is completed, assume that basic upkeep is done by the community as a whole. For example, once the Palisade is built, assume that the steading keeps it in good repair.

Some improvements have additional, ongoing costs, like the requirement to spend 1 Surplus every spring to maintain Weapons of War. If the PCs fail to pay that cost, they lose the improvement. Make a Plan with the PCs if they want to get it back.

You can and should threaten or harm improvements the same way you can threaten anything else the PCs care about. If they don't do something to save it, then it will be lost and they'll lose its benefits. Again, Make a Plan with the PCs if they want to get it back.