Oil paintings should last for hundreds of years, careful handling and attention will give your newly purchased painting the best chance of a great long life!
Handling: An oil painting needs careful handling and needs to be protected from sharp objects that can tear the surface. This also applies to anything that could put pressure on the surface and stretch it out of shape. The canvas can become 'bruised' or dent with surprisingly little force, so be super careful if leaning the painting against anything that is not a flat wall. (I have almost had a mishap when leaning a canvas against an innocuous-looking storage bag, luckily I noticed in time that it was bending the surface of the painting slightly.)
Be careful when you handle the painting, that nothing you are wearing (buckles, rings etc) could scratch the surface. Lift the piece from the two sides, so you don’t accidentally tip the painting and knock it against anything. Avoid door handles like the plague, they can catch and tear your canvas. (Ask me how I know)
If you ever do have an accident, don’t panic. Oil paintings can be restored by a professional, to the point where you would never know there was a problem. But it’s best to save yourself the stress and expense of that!
Lighting: Although all of the premium quality oil paints that I use are certified lightfast and therefore my paintings will not fade, it is nevertheless always good practice not to display your painting in bright direct sunlight. The best lights to use for illuminating a painting are designed for the purpose, otherwise, diffuse lighting is a good choice.
Temperature: Try not to hang the painting in a place where temperatures are likely to fluctuate. Lots of changes in temperature could potentially warp the wooden stretcher bars that support the canvas. The ideal highest temperatures are 65 to 75 degrees Fahrenheit. Keeping the range of temperature that your canvas is exposed to within a 20-degree limit is ideal.
Humidity: (Don’t hang it in the bathroom) High humidity in the atmosphere can cause the canvas to stretch and become less taut on the frame, and is best avoided. If your canvas does begin to 'sag' then it can be re-tightened on the frame, you would just need to visit a framer. It is a good idea to keep paintings away from humidifiers and heaters if possible, to be on the safe side.
Cleaning: If you want to clean the surface of your oil painting, it is possible to clean any dust from the painting by using a very soft brush or white soft cloth. Go gently, and avoid knocking any texture areas off of the surface of the painting. Dont be tempted to use any cleaning sprays or solvents at all as these can damage the painting. If the painting requires more cleaning, then you can use a little warm water and olive oil soap and very gently clean the surface. Only use a slightly damp, not soaking wet, cloth. Do not rub, and dont use paper towels or anything abrasive.
If the painting needs more cleaning than this, I would consult a professional art restorer for advice.
I really hope you find this article helpful.I will also put together a guide to storing and transporting original oil paintings on canvas, and post it here.