property line over neighbors property. Neighbor bought property knowing this years ago

I don't know what you question would be.  If the property line was clearly distinguished in a survey and title report, and the purchaser bought the property that way, and has not said anything, then over time, the property line could be changed .  If the new owner now disputes your encroachment, the new owner could enforce the correct line and require you to move anything that goes over the line.