Best option for excluding read-only tablespaces.

Hello, I think I have found 3 ways to exclude read-only tablespaces from backups:

1. configure exclude for tablespace xxxx;

2. configure optimization on;

Or while doing the backup:

3. backup database .... skip read only;

Any thoughts on preference to one over the others?

This is my particular situation. I have 2 read only tablespaces. Once a month I have a job that alters tablespaces to read-write and moves a partition into the tablespace and then switch it back to read-only. I have daily incremental and weekly full backups for the whole databases running. My goal is to only backup the read-only tablespaces when necessary (initially, after the read-write/read-only switch, if the backup gets removed from disk).