I've heard and read a great deal of debate and discussion among artists on the best methods for keeping their paintings from deteriorating over the years. They heatedly discuss proper supports, materials, grounds, types of gesso, the light fastness of paints and a multitude of other methods and proper procedures.
While good craftsmanship is essential to good work of any type, the single most important thing you can do to make your art last for centurys is to paint great art! All the greatest materials and methods and recipes in the world are not going to make your art last if it's in a dumpster. Your art needs to move people save it, to pass it down to their children, or for somebody to buy it, hang it up and love it. If it moves someone they will take care of it no matter what it was made of.
Look at all the paintings that have lasted for centurys, they are almost all masterpieces. Is this just coincidence? Are great painters the only ones that used sound techniques? Did lesser painters use "student grade paint's" on cardboard - so that no "average" art has survived? Many masters like Da Vinci experimented with fugitive materials and paints, but are still around today.
The reason great paintings are with us today, is because they are great paintings, not what they are made of. Great pieces of art that motivated people to keep them, take care of them and love them through war, famine and all manner of things that would have destroyed even solid steel! I am willing to speculate that the there are thousands - maybe hundreds of thousands of paintings that are gone despite the fact that they were made to last forever and used impeccable materials and paints.
So if you wish that your paintings to last a long time - make great paintings.