How long (after explant) until pocket closes up?

Thank you for the question.  The answer depends on how the capsule was handled.  If it was removed entirely, then the pocket closes in weeks to months.  If it was left in place, it can take many months or never close.  Discuss with your surgeon.

It will most likely take several months for the pockets and breasts to fully heal after implant removal.

After implant explant all must heal together  and allow no fluid to form.    The pocket should be compressed with elastic wraps.  Where there is too much activity or no compression there can be a seroma collection with short or very long duration. Elastic wraps  hold sides together.   If  a long time seroma occurs a reoperation for seroma containment may be necessary.   Generally the pockets are reliably closed in 3 to 4 weeks.   My Best,  Dr C