Is their any long-term side effects of women putting make up on for years and years?
There are many different conditions that contribute to the effect makeup usage has a person's skin: their skin sensitivity, the brand of makeup they wear, how often they wear it, how long they wear it when they do, how and how well they remove it, etc. etc.
Some people will have break outs of acne when they wear certain brands of makeup, when they wear it on certain parts of their face (ex. around the nose or on the chin), if they wear it too long, if they sweat excessively while wearing it, etc. etc.
On a grand scale however if a person is conscious of the ingredients of what they are putting on their skin, long term side effects are rarely seen. Organic cosmetics are the way to go in that regard.