There are some flames that are meant to die. I recently bumped into an ex and learned quite a few things from our chanced meeting. I was really moody after we broke up a few years ago and for a short while I had hoped something will prompt a rekindle. It didn't happen, and I don't know exactly at what moment, but I think a few months in I had completely moved on.
Of course you don't quite know the level of progress made until we're genuinely tested. Meeting the person again I realized that I felt nothing. No love, no hate, no desire to get back together nor a desire to get as far away as possible. I just know that the only things that did arise were short, rather brief memories of our times together and the breakup. I don't know how things are on the other side, but from what I saw I'd guess the feeling was mutual.
I think a flame lasts only as long as someone chooses to fan it. If no one is interested in keeping it going then it dies a natural death. But that's just the point, that even one person's effort is good enough to keep the flame burning, perhaps with withered intensity. As long as there is desire and effort on the part of even one person, the flame never really dies and could always potentially be resurrected.
There's a group on Hive that enjoyed a lot of support in the early days. Unfortunately most people who made up the community have moved on from the platform. Yet I continue to see the platform register it's presence because two persons in particular have kept it going. The examples are many. Nothing is really dead until everyone agrees it is.