Audit Logs Retention, export option

Hi,

Love the new audit logs on Defender, I have a question about how long them are kept as we have managed to amass a around 2700 entries on our log already. Is there an option to download them and start over, I’m just worried about bloat on the database and server when the logs get bigger. Not sure where the actually log is stored?

Also I have setup daily emails but I don’t seem to get any, I’ve checked spam.