Article from Australia – remission is defined as being able to discontinue treatment for at least 8 weeks and still not have any reaction to peanut.
This was a group of 162 children treated between the ages of 1 and 10 with peanut flour +/-probiotics, not Palforzia.
The higher your peanut blood IgE level is at baseline, the lower your chance of achieving remission. But there is no clear cut off:

Young children tend to have lower IgEs, which might be why they are more likely to achieve remission according to IMPACT study and others – in this study, the age they started treatment did not predict remission, once you correct for IgE.