Measure the paint quantity, to get it right all the time.

[RKrebs]

I used to be the same way, I would mix and mix and mix, get the right shade, then either throw a bunch out or need more and not be able to get the right shade again. What I have found over the years is that you get it close, then the rest is lost in the weathering process. Dust, oils, and washes end up changing the colors anyhow. Not to mention, no two vehicles were the same after sitting out in the sun. Not to mention, as someone above said, the paint manufacturers were never able to get the paint the same in each can in the 30's and 40's. Only recently with the aid of computers and advanced paint mixing are they able to achieve the exact same colors between cans.

The long and the short of it, I don't sweat it anymore. But that is just me.

 

[Jakko]

my fingers are too arthritic to tolerate ten minutes of stirring!

I must add that it does depend on the colour. Some form a thick layer of pigment sediment in the bottom of the tin that you have to stab to pieces with a cocktail stick before you can even begin to stir, while others that are just as old can be stirred right away and be usable within two minutes instead of ten or more.

All in all, I don't use Humbrol paints much anymore, but still enough that when I come across old tins of it (which means from before the "Super Enamel" range they introduced about 25 years ago), I always check if there are any I can use. At a model show last February, for example, I purchased the ones you can see in this photo:



All of them are old to ancient (1990s down to '70s production, going by the tins) but I have no reservations about using them still However, only sparingly: for washes, drybrushing, etc. I don't paint whole models with them anymore.