AFAICT, the only way right now to get the oldest listen for a user is to page through /1/user/(user_name)/listens until it reaches the end.

It could be good if max_ts and/or min_ts would accept a magic number (e.g., -1 which seems to be used in the web interface?) to go straight to the max’est or min’est possible value.

Alternatively (or additionally?) an endpoint similar to /1/latest-import could also help with this. (Maybe "/1/earliest-import" – or "/1/user/(user_name)/earliest-import" since you shouldn’t be able to POST-update it.)