I don't believe most can detect any difference in quality from 10 to 12, though file size goes up a lot above 10.
I usually don't worry too much about such things as all masters I have are 16-bit ProPhoto RGB TIFFs, and I create JPEGs of various size and quality (and convert to sRGB) as needed from them. If I want a high-quality JPEG for transport or something to show someone, I use baseline standard, quality 12.
Dunno if that's a method to follow or not