the life line does not indicate how long you will live but the quality of your life. for example a person who has had a lot of health problems in their life will find a chain-like line on their hands.a split in your life line could indicate an illness towards the end of life but you will have to consult a proper palmist to find out if thats what the case or not.
Sounds like your fate line combined with your life line. You should talk to someone who has real experience with palmistry, they would be able to better explain everything to you.
As for gay_wizard, you can tell roughly the length of life if you break the line into the three segments and read it as childhood, adult hood, and old age, and then based on health concerns and the rest of the lines, crosses, etc.. from around the life line area, you can get rough idea as to how long the person will live, and what their quality of life will be.
One quick reminder, the lines on the palms change, at least once a month, sometimes more and sometimes less. Talking a truly experienced palmist will give you more information.