Absolutely agree with you and my procedure is very similar to yours. I use a good 'ol RS analog SPL meter on a tripod at the sweet spot. My Anthem AVM 30 pre-pro is too old for auto set up but new enough it has built in white noise generators that allow for adjusting the levels.
I start by adjusting left front to 75dB and then cycle through the menu for the other speakers to match too. Altho the speakers are carefully measured & set up to be equidistant from the sweet spot epicenter the right side speakers are closer to the wall then the left side. And behind the front speakers is wrap around floor to ceiling convoluted polyurethane for reflection absorption:
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So this arrangement would never sound balanced if I just set all the balance controls at neutral. Tuning it up this way gives me a known value to return too & easy peasy to adjust balance on the fly using the Anthem remote. I set up the subwoofer using the built in rumble tone & the result is always a subwoof that never interferes with the music, or movies, but thunder when real bass is there.
On a device like the Surround Master V2 I have it has individual level pots on each ch I just make a QS encoded file of the main speaker positions & use that set the SM output levels.
And like you I recheck maybe once a year to see if anythings changed. I guess I just like messing with this stuff.