I am not a needle valve fiddler. I sometimes do notice that the first run of the day is a little different than the rest of the runs, not enough to bother, but enough to notice. Generally, If I am putting an engine up for a while, I will squirt some Rislone through the NVA. I think this stops the congealed castor oil in the spraybar. Several years ago I did the same trick you did, tried a wingover with the engine running too rich. So much for that!
I generally run Sig Champion 10% nitro, 20% oil, half and half. I have, a couple of times, run the same mix in another brand and had to make a radical change in the needle setting.