Z setting default value

I apologise if this has been covered but was unable to find a cure.
I have a X35 Woodworker which has worked flawlessly this past year. As time has moved on I have become more particular and as such noticed that each time I power down the system the setting for the z defaults back to 15.4mm. My setup block is 15mm. As such if I do not cater for or change the setting each time I power up I have a 0.4mm over cut on my workpiece.
Is there any way to retain the setting of 15mm as the default?