But what if they move to another county?  Wouldn't it be too easy for folks to fall asleep at the wheel and never update those things if it just rolled over?

(My details box did not open, so I could not add the following.)

It's rather rare for my regular clients to move. But when they do, we always update the ADDRESS in the Information Sheet, which will alert me to update the county. Similarly if there is a sale of residence on Sch D. Additionally we could have a box that simply asks whether the county has changed, the way we do with the driver license box or state ID box. That's much faster than having to open the prior year's tax return, go from federal to state, scroll down to the county, move back to current year, and and enter it in the county line.

"It's rather rare for my regular clients to move."

But you aren't the only preparer in that state using ProSeries 😀