Hi @hfoster, You are right, it is a wonderful feeling to feel normal again when you are dealing with PMR and a respiratory issue as well. I think this is a good question to ask your doctor since there might be other factors involved. I did find this information that speaks to the topic a little but doesn't mention bronchitis.

"How long does a steroid shot last for upper respiratory infection?
Steroid injections start working quickly and usually last for a long time. You only need to get another one if your symptoms return, which can happen anywhere from 3 to 12 months after the first injection. However, many people never need to get another injection."
-- Steroid Shot for Sinus Infection: Benefits, Process, and Side Effects:
https://www.healthline.com/health/steroid-shot-for-sinus-infection
I've had severe bronchitis before and it is the pits. If it were me, I wouldn't taper down until I was sure I've recovered from the bronchitis but I would still ask my doctor about it.