Oracle - Scan listener and multiple databases

I have a two node RAC database server hosting 8 databases. I have 3 scan listeners running. 2 in node 1 and one in the 2nd node. All the 8 databases are running for different applications. Are these 3 listeners sufficient to manage the work load for different 8 databases? So only the service names will be different for the databases for the respective applications to talk to right? Are there any best practices to have more scan listeners run on different ports or or is it recommended that way?