Tim, I haven't chased to lands in a barrel in a long time. Slow, progressive wear is hardly noticeable in terms of tuner setting. Temp changes mask any small difference in tuner setting over time.
As for how often I move the tuner, it's not often nor far. If you see me twisting more than a mark or two over the course of a day, something is wrong. But, temp changes are by far the biggest factor in condition related changes in tune. I'm not one who believes that there is some magical window where temps stop affecting the the chemical reaction that takes place during smokeless powder combustion. There are areas where the gun is tuned that are wider than others in terms of harmonics, though, where tune changes less with equal temperature change. Still, the barrel never stops moving and temp never stops changing the way the powder reacts to those changes, imho.