Is keeping activity on a cc for the cc company or for your credit score?
Does activity have to be monthly or annual?
A card issuer may close a card because of lack of activity.
You don't want cards closed because losing the credit line may impact your credit score.
So: Use your cards periodically. IDK how often, but less than monthly is necessary.
OR: Close your card yourself and move the credit line. Either to another card from that bank, or use it to open a new card.
Note: The hit to your credit score from losing the credit line is usually small and will disappear in a month or two.
I think your making it a bit more complex then necessary.
To answer
@lcm keeping activity annually is for the credit card company, which will close your card otherwise.
If your looking to help your credit score then using it monthly, while closing your statements at $1 as Dan suggests is the best way to go.