Exhaust Technical Question

I am looking at purchasing a Slip On exhaust (for an ER6F) and have seen many posts abouts the sounds of exhaust and the popping noise and associated PAIR valve fix, etc. However when browsing online for different exhaust I noticed that the Scorpion for example mentions:
OK so I believe I understand the re-jetting/re-mapping... but what is "repacking"?
Do some exhausts (only talking slip ons) require some form of maintenance?
High quality and high-performance mufflers with model-specific design; requires no re-mapping or re-jetting. Never requires repacking.
OK so I believe I understand the re-jetting/re-mapping... but what is "repacking"?
Do some exhausts (only talking slip ons) require some form of maintenance?