How long is advair diskus good after the expiration date?

I think so since the seal has not been broken

Advair diskus is a combination medicine used to prevent asthma attacks. It is also used to prevent flare-ups or worsening of chronic obstructive pulmonary disease (COPD) associated with chronic bronchitis and/or emphysema.
The expiration date on Advair diskus is the final day that the manufacturer guarantees the full potency and safety of a medication.
Because these conditions are potentially quite serious Advair diskus should probably not be used after the expiry date. Best to get a new prescription.

https://www.drugs.com/article/drug-expiration-dates.html