Managing signed git tags and expiring keys

Howdy,

My question is about the Git workflow in a repository which has signed tags and uses expiring keys in a chain of trust.

When the key changes, all existing tags are signed with the previous key in the chain of trust.

Do people:
1) resign all the tags, causing people to overwrite their local tags
2) keep all versions of the keys in the chain of trust
3) something else more involved?

Is anybody doing this currently?

Thanks!

Duke