This may be a bit off topic but, I completely disagree, with anything that requires calibration of one type or another over time and use, calibration needs to be checked and adjusted periodically. It may not be the OP's issue here over such a short period of time but, then again it's possible. Depends on the equipment, the environments it's used in and the handling it sees. For example just moving a camera and lens from cold to warm environments will cause changes and movement within both the body and lenses, along with components in the assembly wearing in. Over time that movement will gravitate in one direction or another from what would be considered absolute zero when properly calibrated. Go to any machine shop and you'll see calibration stickers on every measuring tool with dates as to when it was calibrated and when it's due for it's next calibration. The more intricate any given system is the easier it is to throw out of calibration, in other words the more complex the more that can go wrong. The last time I checked, auto focus lenses are a bit more complex a system than say a micrometer.

I do not know why you had to calibrate focus for your 18-140 VR lens. I cannot remember when I had to do that with any of my lenses. If I happen to see any discrepancies in the focus of any of my lenses I would prefer to take camera and lens to a technician for calibration but that is me.
Since I have never done calibration of any of my lenses useless to say I do not have the experience to discuss this matter but as I already said, if I note any discrepancies in focus I would prefer a professional to do the job for me.

This may be a bit off topic but, I completely disagree, with anything that requires calibration of one type or another over time and use, calibration needs to be checked and adjusted periodically. It may not be the OP's issue here over such a short period of time but, then again it's possible. Depends on the equipment, the environments it's used in and the handling it sees. For example just moving a camera and lens from cold to warm environments will cause changes and movement within both the body and lenses, along with components in the assembly wearing in. Over time that movement will gravitate in one direction or another from what would be considered absolute zero when properly calibrated. Go to any machine shop and you'll see calibration stickers on every measuring tool with dates as to when it was calibrated and when it's due for it's next calibration. The more intricate any given system is the easier it is to throw out of calibration, in other words the more complex the more that can go wrong. The last time I checked, auto focus lenses are a bit more complex a system than say a micrometer.