O rings in the actuators snap

The Viton O rings in the actuators should last for a long time. They certainly shouldn't degrade due to humidity or UV exposure, like the old elastic bands did. However, sometimes they still snap. My suspicion is that they snap because they've been mechanically damaged during assembly, even if it takes a while for them to actually break. However, I'd be interested to hear from anyone whose O rings have snapped. If you have snapped O rings, it would be great to know:

• How long after assembling the microscope did it snap
• Was the microscope in use when it snapped, or did it snap while it was in storage
• Was the print quality of the microscope (particularly the tops of the actuator columns) good? This is hard to assess without breaking the microscope body, but if you're willing to pull the column out of its casing (the column is the vertical piece of plastic where the brass nut sits) and take a photo, that would be great.