Re-torquing Spark Plugs

[XfireZ51]

Before heading to BG I installed a fresh set of NGKs. They were torqued down 1/4 turn from seating with anti-seize. After about a 1000mile round trip, I removed the plugs just to do a check. Pretty easy to remove as if they backed off a bit. My left side seems to run a bit leaner than the right side. Wish there was a way to adjust fueling in calibration from side to side. It could be my own
imagination, but the motor seems to run smoother and quieter after re-installing plugs and re-torqued. I also noted a couple of plugs that appeared to be running leaner and these needed to be re-gapped. Gap was smaller than the spec .035".
Interested in hearing if anyone else has made similar observations. Also, do you do anything to keep plugs from loosening up or do you just recheck and retorque?