The machine is just over two years old. Keeping a strict maintenance schedule will ensure the machine and sensors are properly cleaned, because depending on the type of sensor, the detecting distance varies, and if the detecting distance is less than 1mm and the sensor is dirty with metal chips, this could result in errors. Also, the life and accuracy of the sensor can be checked and they can be replaced before starting to fail, so the production flow will not suffer.
We have the basic D5, so you are right, no eMax. We use an Origin D40 for wet milling when needed. Since then Datron came out with a model that supports wet milling, so this covers also the Titanium worries, although mist cooling when milling Titanium is possible and it really works. I didn't believe it either until I saw it. It's just a matter of Cam tweaking.
The spindle comes from the back, and you cannot see it directly, but there is a camera inside the machine pointed at the disk, and you can see exactly what goes on during the milling process. I also prefer the machines that give you more access, but not all machines are built and thought the same way.
I forgot to mention in the first post, another big plus, is the blank magazine (8 blanks) which allows you to program the machine to work overnight without being supervised, since the machine automatically changes the disks in the order that that operator programs it.
The machine runs for at least 7 hours a day, depending on how much work there is or depending on the complexity of the frameworks.
I don't remember exactly to the cent how much the sensors cost, it depends on the type of sensor, but off the top of my head, one sensor costs between 150-180 Euro. Until now we changed less that 7 sensors, so I think that's pretty fair, considering the machine rarely rests.
If you have any other questions, please feel free to ask.