How long can a person live with Stage 4 cancer, from cancer that metastasized to the bone?

My mom has a stage 4 cancer. She found out she has cancer stage 1, 8 years ago. Around year 2000. Then this year her cancer has metastasized to the bone on her chest. And is now stage 4. Does anyone now if my mom can still live a long life? I'm really saddened by this but i'm making the most of every day i spend with her.