Yes, you can modify the retention policy of an existing backup job at any time in BDRShield. When you change the retention settings, the updates will apply to future backups and the processing of recovery points.
However, the modified retention policy will not affect previously created backups. For example, if you set a new retention policy to keep only 5 recovery points but had previously accumulated 10, the 5 most recent backups will remain, and older backups will be deleted during the next retention cycle.
It's a flexible approach that allows you to adjust your backup strategy as your needs evolve over time.