The IFS model says that unburdenings are permanent. So if an unburdening is done fully, then theoretically that burden is removed forever from the Exile. This is typically what I see.

That said, if an unburdening was not done throughoughly, an Exile might need the person to go back to really finish a part of the process. Most often this means more witnessing.

In addition, an Exile can have more than one burden. So the Exile could still be a burdened part if the other burden(s) haven't been removed.

Another scenario in which an Exile's unburdening can be "undone" is when that process was not facilitated by Self, but by a Self-Like Part. These are parts that resemble Self because they have similar qualities (like compassion, curiosity, care) but are actually parts and have their own agenda. It can be difficult to identify these parts, even IFS therapists might not realize a client is in a Self-Like Part if the therapist is not alert to the possibility. (More info on Self-Like Parts here - https://seekdeeply.com/ifs-therapy-guide-6-most-common-self-like-parts-framework-blog-post/ ... I'm offering a free workshop on how to untangle yourself from these parts: https://seekdeeply.com/workshop-ifs-therapy/)

Theoretically, if an Exile was unburdened via the therapist's Self rather than the client's, then that part might still mistrust the client's Self.

Hope this helps! Follow up with more questions if you like.