I use my dip pens primarily for writing letters, not calligraphy.
For me, cleaning or not during my writing session depends on the ink that is used.
Thin inks like fountain pen ink, Higgins Eternal or Daniel Smith Walnut ink does not need to be cleaned during the writing session. When I write, I do not stop long enough for the ink to dry on the nib. I just dip it into the ink, and off I go. So for thin inks, I will clean only when changing inks.
THICK inks like Speedball acrylic however is a different story. Speedball acrylic ink dries fast and will cake the nib. Even if I do not "stop to think," I have to periodically clean the nib of the caked on acrylic ink, or the nib will write poorly.
So what I am saying is, it depends, on the ink and how the ink dries on the nib as you are using the pen.