Wawa:
An opening contact is more reliable than a (old/dirty) closing contact.
And a signal wire of a twisted pair that is normally grounded is less likely to pick up interference.Interrupts is for fast re-occurring things, like rotary encoders.
Not needed for a slow end stop, and usually the last thing you should think off.
Polling each loop (between each step of the motor) is just fine, and likely less problematic.
Leo..
I figured checking a boolean value is less time consuming that a digitalRead() call. I could switch to polling inbetween motor steps though later on.