When does an absent parent lose rights to see their child? How long does a parent have to be out of the child's life before they are no longer entitled to see them?

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

Where did you get the idea that an absent parent loses those rights? In fact, only a court can terminate those rights and courts are very reluctant to do so.

If a parent has been granted visitation by court order then that order remains in effect until a court changes it. If no visitation order exists, a parent can go to court to enforce their rights at any time.

However, as a practical matter, a parent who has been absent for many years may have their rights curtailed until they can prove themselves.

If you explain more of your situation we may be able to help more.