Is it typical to live many years using a colostomy bag?

Yes.
It’s of people with Crohn’s and Ulcerative Colitis have long-term colostomy bags.

My cousin had to wear one since childhood, and is now in her sixty’s.

Yes, I know someone who has had one over 30 years, but he did not have cancer.

The wife of my dad’s friend had one for a few months, she did have stage 3 cancer. Two days ago she went for surgery to reverse it, and she died a day later. Something went wrong from the surgery I guess. She was in her 70’s. Maybe it was a blood clot? I don’t know.