Thank you all for the feedback,
Roscolo and Mark: I know what HP recommends, however the fan running all the time is not an option for the intended placement. If I can not find a workable solution, then I might have to drop the Z3100 from my list. However it is more complex then fan yes/no. The build in maintenance is a blessing.
iCrop: It is just this kind of head failure that I would assume will happen more frequently. Still, fear and doubt are not such good advisors and I appreciate your experience report.
Neil: I share your thougths regarding energy savings, it was already very bad with the Designjet 30.
I wonder how likely they will/can add a real sleep mode, (very unlikely I think myself). For the rest I would be inclined to operate the printer like you do.
Harry Carpenter: This of course the positive news I like to read, it is like my old Designjet 30.