The sounds this thread is referring to is a different one, correct.
You'll find a few topics regarding your PTU behavior, better have a look at those if you wish.
Nobody is risking anything, but in order to not be grounded for every small misbehaving system we have something called a MEL where it's clearly outlined what system might be faulty and under which conditions.
Since the job of the PTU is basically to help pressurise either the green or yellow hydraulic system the reason for a constantly running PTU could be as simple as a faulty pressure sensor, so that the PTU "thinks" it's time to get to work. There is a MEL for that which makes you check that the PTU is running properly. It doesn't mention it has to actually stop running at some point, which (if you're trying to understand the logic behind those MELs) it might be doing just for passenger comfort and mechanical long term benefits anyway. But if it does its job whilst running continuously - there's no harm to go fly with it.