Have scotch bonnet and habanera pepper & am about to make g/p tea. Question--can I store it-- & how long --in a used plastic gallon jug formerly used for milk?

Yes, you Don't put it in a glass container and don't use a tight lid.
Better & easier is to dry the peppers and then pull them out to make fresh tea when needed. Much much easier in my experience. Besides, a strong garlic/pepper tea concentrate is VERY fragrant and will affect the area where you store it. I haven't ever found one that didn't.

Hope that helps!
Kathe