Probably one for the geeks among you 
My IMatch 3 software has a validation feature which gives the dE2000 errors for the current monitor icc profile.
These dE2000 errors, in simple terms,  are a measure of out-of-gamut amount of the monitor in relation to the test colour patches. A value is given for each patch and an
average.
I always use the advanced method of calibration which allows you to set the monitor colour temperature with the RGB gain controls which leaves less for the graphics card to adjust via the LUT.

I have been aware for some time that the individual RGB gain settings and the brightness setting combination can affect the validation values, both on my old cheapo monitor and my current Eizo wide gamut unit.
Recently I played with the RGB gain settings on the Eizo monitor to see what could be achieved.
By reducing the RGB (individually) values when the colour temperature is set, and correspondingly increasing the brightness to still get 120CD/Msq, the average dE2000 error went from 0.74 to 0.59. Not much overall but, significantly, the error on some individual colours improved considerably, but  a few got worse.
There is a limit as to how much you can alter (reduce in this case) the gain settings as they go out of range and the optimum setting indicated by the software.
A table from a spreadsheet is attached below: the green numbers show improvement and the red are where the values got worse.
I suppose this shows it's worth using the advanced method of calibration and setting the gain values individually to achieve the colour temperature and to try different RGB values to get the best possible overall result. Once done and the trend is understood, it's then easy to maintain the improvement on subsequent calibrations.
Or is it all rather academic?
Terry.

I now find that the Eizo monitor is so stable that every 3 months is fine.
I calibrated a friend's Iyama 24" monitor last night. There was little scope for adjustment on the RGB values which were up at at 97% and brighness at 100%. l left Contrast at it's native value of 50%. The validation check showed that the result was good with a low (<1) error value.
I'm not sure if laptop screens vary in quality but my Acer 15.5" has a small gamut and is not stable, the calibration seems to go off, based on the validation check, within a couple of weeks.
Terry

Hi Chas,
Because mine is one of their lower cost models, the S2242W, which does not have the hardware calibration feature like the "ColorEdge series. It requires the more conventional software calibration where the LUT is on the graphics card rather that in the monitors own electronics.
The Eyematch 3 software can, I believe, be used for hardware calibration if required.

Terry.

Chas,
No worries, I'm just a poor retired person 
After having a really cheap monitor, even a "lower-end" Eizo is a new world to me, it makes judgement of colour and calibration so much easier.
Terry.