Should the Tone Arm be Removed When Installing Cartridge?

Does the tonearm have a detachable headshell? If so, I see no reason to remove the whole tonearm in order to install a cartridge.  If not, I still don't think it's necessary.  In fact, there is some advantage to leaving it mounted because you can more easily avoid stress on the bearings if you're careful.  On my Triplanar tonearm, which does not have a removable headshell but which does have an azimuth adjustment that permits rotating the whole headshell by 180 degrees, so the mounting surface faces upwards toward the installer, that's how I do it.  Makes life much easier.

No. That is an accurate and legitimate reason to be careful.

Always remember, consider the source. In this case the source being audiophiles, by the time the day is out you will have them saying your whole neighborhood is at risk of imploding into a black hole if you try this without having the electric utility come disconnect power first, and even then only inside a Faraday cage installed within your Class 5 Clean Room three basement levels below the one in The Andromeda Strain.

The task requires some care and agility regardless of whether the pickup arm is mounted or not.

millercarbon, I am not certain of your intended message.  Are you disagreeing with me, in that you think the tonearm should be removed to install a cartridge?  I've never ever even considered doing such a thing, but if I did, I would then be very worried about damaging the cantilever/stylus when re-installing the tonearm. That to me is even a greater opportunity for disaster.  I am not rabid on this topic; it's surprising to me that others might routinely do what I never have thought of doing.  Which is fine.

Been doing it for decades and always considered the arm staying mounted as the third hand needed when the arm did not have a detachable headshell or removable wand like on the Graham 2.2 .
I agree with Lewn, more risk of damage when attempting to reinstall arm with cart mounted.