For people who have the misconception that oil paintings will last much longer than acrylic paintings, please understand that this fallacy could not be further from the truth.* In recent studies, scientists have found that acylic paints stood the tests against atomospheric conditions better than oils. And they did not have to be treated as gently as oils when caring for and cleaning the surfaces. While it is true that acrylics have only been around since about the 1930's and oils have been around for hundreds of years, scientists have sped up the process of how heat, temperature, and care all affected these two types of paints in labs and they were genuinely surprised to see that the acrylic paints did not break down or fade and crack in high temperatures as the oil paint did- in fact acrylics were more stable. *
I believe this is in part due to the apoxy substance that is added to the acrylics in manufacturing. Once acrylic paint dries, it is waterproof and can withstand heat and high temps where oils cannot. And as far as care, oils must be specially cleaned so the surface will not fade, crack, or mold, where acrylics can be gently cleaned with water.
I firmly believe that if acrylic paints had been readily available for many of the great masters, they would have gladly switched to acrylics over oil paints because of the versitility and ease involved in using them. And acrylics are less expensive too, which would have made them even more appealing.
So if you are browsing through the paintings on Ebay and see an oil painting that is priced rather high, please know- it isn't because the paint is any better, it is just because the paint is higher in price and takes longer to work with. In fact, art is art, it is an expression of the individual creating it in reference to the world around them or the conditions of their inner self. And for whatever reason you like a painting or drawing, maybe it reminds you of your childhood or makes you feel relaxed, don't hesitate to purchase it, because it spoke to you and that is all that really matters.
* This information is based on scientific research done by Getty Conservation Institute.