Not to be argumentative, but, I have saved empty bottles and tins all my modeling life, and I have used them over again to store everything from custom paint mixes to small working quantities of the other liquids used for modeling.
I see where your findings could be true for me here, if I built differently. If I built one Zero, with correct colors, and then one FW-190, and then one USN Hellcat, and then one camo'd P-40,,,,,just in those four models a lot of colors would get stranded. (and never used up)
But, I am building Hellcats, Corsairs, Blue Skyraiders, etc, by the dozens (total), and hundreds of Light Gull Gray over White aircraft,,,,,,,,one bottle of Gloss Sea Blue at a time (or Light Gull Gray) isn't going to cut it. I am not sure I have enough paint as it is, with 700 "active" bottles (I gave away all the colors that I don't need)
And yes, paints dry in their bottles,,,,,,but, that is mostly a manufacturing thing, the packaging isn't sold to us in a design "built to last" (I've posted the "right way" so many times, I am sure people are bored reading it by now)
There is just nothing worse than getting 100 aircraft into a collection with all the "right" colors, and then finding that you can't buy them anymore before you build the other two thirds of the collection.
Rex
ps, LifeColor is sold in 22ml plastic jars (1 and 1/2 times the size of Model Master), and you can get almost all of the "colors from sets" separately