Finally figured, after destroying several of them, what it takes to
toughen them up.

Several months ago, I also caught one a sale for half off. I have two
prime working units.

The trackball unit has four click relay buttons, assignable with
Logitech software to goes back to mythological ancient history:
Pre-XP and XP Logitech software drivers still work on current Marble
Trackball iterations.

They're paired buttons. On the right-most, the largest surface area
and main button;- above and near the center apex, the so-called
palm-resting area, is one of the two small buttons, perhaps a 20th the
size smaller of the former.

Use the software to define *both* these buttons for the Windows
main-selection mouse action, whereas on the other and left side,
define the larger of the two for the properties-button Windows'
assignment. The left smaller button is actually inaccessible, poorly
thought-out, for any practical intent and difficult to intuitively
locate from finger memory.

I'm right handed, but place the Trackball to the left of the keypad,
which I found best to accustom myself to this arrangement.

That right-most and smaller of the two button, anyway, I suspect may
be a sturdier anchor design placement and one less prone to fail
tolerances, intermittently to cease to work, as is the case with its
counterpoint, the larger-area actuator.

Additionally, is to consider, when the smaller does eventually fail,
by not using the same-defined larger actuator, at that point,
switching to the larger would serve for a secondary and back-up
Windows main-selection button.

Since I'd formerly replaced mine every year, to two years and hardly
more, after the larger indeed did fail, this arrangement promotes to
auger twice the possible longevity for continued usage.

Any longer, I simply haven't the patience to deal with Logitech,
which, after the rigors of automated web services, variously to some
extent, is favorably disposed by design to filter some product
dissatisfaction. That being said, it is then easily enough
determined, having duly followed and dealt from a web-centric Logitech
CS, they will regardless compound advantage from return shipping
charges the company administers to dissatisfied customers.

Other, that is, than to qualifiedly temper this Trackball as the only
decent one made in the world that I care to use from a $15US sale, at
half off, on the back-up unit I from prior experience am now adamantly
anticipating.