query: when does being threatened with adverse possession end

I do hope you confer with a good real estate attorney.  In PA, you can evidence that you granted permission for the use, even if temporary permission and that should defeat an adverse possession claim.  A good real estate attorney can advise you.

I bought a property a few years back and the survey revealed that a neighbor was using my land for parking and generally as a side yard.  The land was on the other side of a creek and if I had not had a survey done, I might never have know it WAS my land.  Interesting, eh?  Anyway, I visited the folks and offered to sell them the land for a small amount plus the cost of doing a subdivision.  They said no, so - to protect myself from an adverse possession claim - I sent them a letter giving them temporary permission to use that portion of my land.  That was all I needed to do to defeat a potential adverse possession claim. 

Some readers might say what's the big deal?  Well, if I am paying taxes on the lot, I want to maintain control.  The neighbors wanted use but were unwilling to pay, so that's life.

Adverse possession is a real threat to property owners and you should take the simple precautions available to you in the law.  Ignoring the use of your property by another is not an option unless you don't care about the loss.