I believe that is what the airport is currently doing - last night seems to be a one off, having just one (I presume tower only due to the NOTAM), controller on shift. There was a further Notam sent extending the radar hours until 2245z, probably due to the late running Globespan and a couple of FRA Falcons I heard going out about 2100z.
Thanks Bol Zup, for the information regarding current staffing levels.