Olive leaf powder for tea preperation

Wanted to ask if the olive leafs lose their benefits after a while following the below preparation method.

After picking the leaves and drying them over a period of a few days, I would grind them in a coffee grinder, and put them in a plastic bag, then would use about a table spoon to sink in hot water to make the tea. the bag usually lasts a couple weeks- 1 month.

1. Would leaving the powdered olive leafs in the plastic bag over a period of a few weeks until used could negatively effect their potency?
or its better to grind them only before making the tea?

Ans; This way will be fine, as long as the leaves are dry.

2. I sometimes get small pieces of the olive tree branch grinded along, it gives a little bitter taste, it that ok, or i should make sure only the leaves are picked individually?

Ans; This is no problem as the twigs also contain oleuropein. It is more a matter of taste.

thank you!