How often do you need to tighen your hitch ball?

There are whole college level courses on fastening methodology (part
of my strength of materials classes) and can not cover it here, but
the essence is that the designers have chosen via calculations and
empirical data the proper sizing and torque (that should be on the
ball's packaging)

Here is a good site that has most of the germane info:
Bolt Science..info page

Or you can go 'farmer tight'... :S

Part of the science is to preload the bolt (the balls threaded shank is that)
so that the clamping force (shear and tension...clamping are the some of the
things it does).

In consideration of the application and possible worst case vibration
and other forces...so it should NOT come loose if tightened to spec

That clamping force is to keep the ball from turning and moving around in the
hole.

My guess is that your ball packaging will list something in the 400-500 ft/lb range.
A four to five foot long breaker bar with 100 lbs at 12 inches from the pivot


Suggest you take the shank & head to a RV or good mechanic shop and ask them
to tighten it. Some will do it for free...others for not much $$$