The main question here is âDoes it affect your printing?â
Iâm never against improvements, but they have to be kept in perspective of the ultimate goal youâre trying to achieve here.
Otherwise youâre just âchasing zerosâ for accuracy with diminishing returns.
Case in point, Hotend temps.
Ultimate goal: Melt a thermoplastic past itâs glass transition temp to extrude it.
Glass transition temp isnât a sharp cut off point, Itâs a smooth curve.
If you look up a glass transition temp, Itâs just giving you the glass transition POINT (where the region begins) and it always says âApprox x degreesâ or â~x degreesâ because there is wiggle room and then past that point youâre within the transition region for a relatively wide band of temperatures.
but still seeing ~0.4 deg fluctuations
Thatâs an outstanding level of control. The ultra highest accuracy PID controllers used in labs and metrology only claim .1% accuracy
At 230c that would be 230 * .001 = .23 c fluctuation, youâre double that but still, youâre better than most industrial controls tuned by professionals that get paid to do it with the best equipment.
itâs 1-2 deg fluctuations all the time.
Nature of the beast, you tuned for one temp, if you go outside that range you will get variance. 2 degree fluctuation at 230c is .8% (Edit: Itâs .87%, or closer to .9% since weâre chasing accuracy here 
) , less than a 1% variance. Thatâs pretty awesome and well within glass transition temp.
If you were fluctuating 20 degrees or so, thatâd be a MUCH bigger issue.
All in all, Your PID is doing itâs job and is on par with some of the best out there.
Again, It all comes down to⌠âHow is it affecting my printing?â