We were diagnosed years and years ago, but several of the host parts really struggled with accepting the diagnosis for a very long time. After that they still went back and forth between acceptance and denial over many more years.

I think how long that takes may be dependent on one's individual circumstances, particularly when current day contact with perpetrators is involved. If there is ongoing contact with abusers it may take much longer to work through the issues, whereas if there hasn't been contact with perpetrators for many years it may be much easier to accept.

In my own case we had ongoing contact with abusers, so it was still necessary to maintain the dissociative defences... which meant, for some parts, not accepting that the dissociation (and thus the abuse) was true.