I wondered about that. I was afraid to turn those adjusters more than a quarter turn because it has to affect mixture throughout the RPM range. If I lean the mixture out at idle, it may be too lean throughout the rest of the range.
That is a concern; and I suspect is sometimes the source of overheating problems (caused by mixture too lean at cruise conditions).
Part of the problem (IMO) is that most rebuild kits do not include new jets and needles, so many don't replace them. In theory, they shouldn't need to be replaced, but in practice both of them can wear if the jets are not perfectly centered or the piston rod & bearing are worn. And wear is almost impossible to judge.
Note that if the upper gland (the cork washer inside the jet housing) is leaking, it leaks fuel into the carb throat.
Also worth noting that the "lean" needles do not idle leaner than the standard ones do, the lean mixture is in the mid-range.
At least in my experience, throttle shaft wear doesn't upset the mixture too much until they are really badly worn (enough to cause other problems).
Make sure your jets are centered. If you lift the piston with a finger and let it go, it should land with a distinct click. The motion is slowed by the damper (if you have it installed), but you should still get a click. If no click, the needle is rubbing on the jet, which will upset the mixture.