OT - Alkyd paint shelf life

[Hendrik]

I use alkyd paint (one component) on my wooden doors, window frames, etc. (house exterior). I have some paint that is three years old, in a well closed metal container. Needs only a few percent of thinner and thorough stirring to make it perfectly brushable.
What I find is that it dries/cures VERY slowly. (Where fresh paint takes a day to dry, the old stuff takes three to four days.)
Should I be less frugal and discard the old paint OR can I use it as is?
Thanks for any and all comments. Hendrik
 

[Stephen Newell]

I have paint that is 15-20 years old I still use. I sometimes add linseed oil to it to rejuvenate it especially if I have to break a 1/2" thick layer of dried paint skimmed over the top. More than likely the problem you are experiencing with the paint drying is from thinning it. Paint thinner alone will make an alkyd dry slower.