In an effort to maximally control light bleed on long prints, I have my shutter setup to be closed whenever I am not actively projecting (layer changes etc). This means my shutter actuates.. a lot. So much, in fact, that I wrecked the original stepper. My fixing of that stepper is documented elsewhere on the forums, but unfortunately the problem returned. My fix worked- the stepper wore out elsewhere in the mechanism. Oops! Analyzing the failure mode(s) of the stepper tells me that this much actuation will wear down the stock stepper sooner than later.
Thus, I have done two things- replaced the stepper with a superior model, and replaced the shutter. The stepper is an MG996R, and the shutter is a smaller, thinner one. I'm quite pleased with the results! My new 'design' weighs in at almost exactly half of the stock model, significantly reducing strain on the stepper and speeding up actuation a bit.
See the imgur link for some pics: http://imgur.com/a/3QqTW
I have enough plexi to make a few more if people are interested. I can also order some more and make some to send out. I'm guessing they'd run maybe $15 incl. shipping. Maybe less (definitely less if more than a few are interested)..