There doesn't seem to be any automatic cleanup of the data being generated by performance advisor. Should there be? Out of the box Windchill log files are automatically cleaned up after 30 days. Maybe a similar approach should be taken for the performance advisor data. Are others manually purging this data occasionally?
I think it should be safe to delete data in create folder, because they are the same that are written in sent folder after they are successfully sent to PTC site.
Because data in the dashboard are of the last 91 days (13 weeks) I think that automatically, like you said for Windchill logs, they should be deleted in Performance Advisor folders after a similar period of time