Ublox 6 gps receiver saving settings.

I have a ublox neo6 thats been sat in a drawer for a while.

I want the oscillator to o/p 10kc which it does, I configure that in the config view/timepulse 5 window, then I save settings in the configuration window.

If the unit is then powered down for a while and powered back up it comes back on with 1pps instead of the 10kc I setup previously.

How long does the backup batt last in these?, or am I doing something wrong in the save setup.