If you are asking how long betrayal trauma lasts, you are probably asking because you are still in it — and because the world around you has started to suggest, directly or indirectly, that you should not be. That enough time has passed. That it is time to move on. That you are holding onto something you should have let go by now. And you are sitting with the gap between what they think the timeline should be and where you actually are.
The honest answer to how long betrayal trauma lasts is this: it lasts until the conditions for healing are in place — and not a moment sooner. Those conditions are specific. Safety: being out of proximity to the person or situation that caused the harm, or having clearly established that the danger has passed. Honest grief: naming what happened accurately, not minimizing it or compressing it into something smaller than it was in order to get through it faster. And time: the slow, unscheduled process of the nervous system learning, through small consistent experiences, that closeness is not always dangerous.
None of those conditions can be manufactured by deciding to be better. The nervous system does not respond to determination. It responds to evidence — slow, accumulated evidence that the world is safer than the wound taught it to believe. That evidence takes time to accumulate. And if the safety has not been established, or the grief has not been real, or the wound has been reopened repeatedly by contact with the person who caused it — the timeline extends. Not as a punishment. Simply as a fact.
There is also the compounding effect that most people do not account for. Betrayal trauma rarely arrives cleanly. The original wound is followed by the grief of lost trust, the disruption to other relationships, the secondary wounds of people who responded badly or not at all, the legal or financial aftermath if those were involved, and sometimes the ongoing presence of the person who caused the harm in shared spaces or through shared connections. Each of those is its own wound on top of the original. The timeline for healing all of that is longer than the timeline for healing any single one of them — and it runs on the pace of the most significant piece, not the average.
What tends to help is not accelerating the timeline but accepting that the timeline is what it is. The wound is not a character flaw. The duration is not a measure of weakness. The person who is still carrying betrayal trauma two years, five years, a decade after the original harm is not someone who failed to do recovery correctly. They are someone for whom the conditions for healing have been hard to establish — and who deserves support in those conditions, not pressure to perform a recovery they have not yet had.