Any further thoughts....it is definitely not that the batteries are going flat - far from it as they all remain at 1.2V (and are new as well).....is it possible to alter / hack into the firmware code and change the setting ?
Surely I can't be the only person who finds it ridiculously irritating to HAVE TO re-charge it every night .... and as I have now had a total of 4 TSU700 / RU980 / RU990 units they can't all be faulty !