Yikes. That is not a very good lifetime. In most cases, with regular plotting duty cycles, servos last from months to years. However, some individual units do fail sooner. The most important considerations, as I already mentioned, are the conditions. Heavy duty cycle (constant up/down motion) can lead to heating, and that can lead to overheating under certain other conditions.
(I don’t have a date on it yet, but we *are* looking into servo alternatives for the future– hopefully we can end this once and for all.)
The AxiDraw should be connected to your computer through USB, which provides the grounding. If your computer is plugged in with an ungrounded two-pin prong, that is a potential concern. I have not heard of any specific issues with the belt building up a charge.
Lenore will follow up with you separately about the servo replacements.