Do you mean sleeping too long as in more than the standard 8 hours.... or sleeping too late into the day like I went to bed at 2 am and got up at 10 am?
Everyone has their own internal clocks and your body will adjust- imagine those that work overnight and sleep during the day......
I've read quite often that there are a long list of dangers to sleeping more than 9 or 10 hours a day including heart attack and diabetes with an increase of risk up to 50% more. It's just crazy to think about what people could be doing to themselves!
Habitually go to bed too late, like you went to bed at 2 am, if frequently, could have high probability causing liver cancer. At 11 pm to 1 am, we should be in a sound sleep, so the liver can perform detoxification. When we are not in a sound sleep, the liver has no chance to repair itself. For a long period, it will cause damage to liver.
Sleeping so late and waking up too late will disrupt the process of removing unnecessary chemicals. In the morning 7 - 9 am, stomach is on duty. We are supposed to feed stomach. Then at 9-11, spleen is on duty. It converts the breakfast we ate to blood and energy. When you miss breakfast and has nothing to convert to blood and energy, for a long time, it will cause pre-matured aging. This is all because every two hours, the body has a scheduled bio routine/remedy.
I used to think as long as I got 8 hours of sleep, sleeping late or not, does not matter. As I read more, I realized the same 8 hours of sleep, at regular time v.s. late night are very different. Think the bio clock is like four seasons. A plant needs 6 months to turn into flowers or fruits. Plant it in Spring is not the same as plant it in the Fall even though giving it the same 6 months to grow.
Please use key words "liver cancer and sleep" on search engine to learn more about sleep and liver health.