Dion has a solid point that inside does have better performance especially in unstable room temps!. I don't like to use tape inside so I hot glued mine to the floor of the enclosure. I torture tested the probe and found that I can't lift it or shift it off the floor, it is unlikely a Royal Python could ever do so (a retic maybe...) The other concern is poop on the probe will generate a false return the unit. I use a back up on off (great use of a hydrofarm) with its probe on the uth and set high so if this does occur the herpstat will power down before over heating occurs.
I have never had that happen and I am not totally convinced of the need as the poop will be the same temp as the core temp of the snake and may not ever cool off to that point.