I can change a cartridge and set up the replacement in twenty minutes. If I change the headshell on the one tonearm I have that uses interchangeable headshells, it takes about 10-15 minutes including the set-up of the new cartridge (the SME 309 headshells don't allow for individual overhang: that must be set by moving the arm, which is pretty simple on an SME mount). It isn't that big a deal, either way. What does matter, is that even if I achieve a 10 minute change and set-up, I cannot compare the before and after: my auditory memory is not that long.
So I approve of your two tonearm advice, with one arm capable of holding multiple headshells. When my custom Acoustand panels arrive, I'll be using four fixed headshell tonearms, and two interchangeable headshell tonearms.