I guess you could create a cron job that runs just after the start of a new epoch and appends the output of that command to a file for later viewing?
When Jormungandr is restarted you loose all the leader logs for previous slots your pool was elected for. So you probably need to keep your own log.
Would be interesting to hear from the official devs if they plan on some kind of log system which caters to stake pool operators interests. For example an archive log containing a historical list of slots the pool has been scheduled for and the blocks status (sniped, missed, successful) etc.