I think if a field in a JSONB column is used frequently in the most common query patterns, it might be time to "surface" it up among other non-JSONB relational columns. There will be some additional overhead e.g. it should be made a read-only column for consistency's sake; if you update the value of this field in the JSONB column, this surfaced column should also be updated.

However, a bit of duplication is not a terrible trade-off for significantly improved query performance.