The Verify files operation is documented in Verifying backend files as being just the tiny sampling test that happens after each backup, so pushing the button adds little. You can increase the sampling:
backup-test-samples
The TEST command
but in any case this is mostly a test that remote files have the expected content, by downloading them.
There’s no substitute for testing a Restore, and how heavily and how often depends on how important your backup is to you. Maybe it’s not, maybe it’s a secondary, maybe it’s primary and super-important?
It’s up to you and depends on time available and maybe download costs or limits, but I recommended
Or if the backup doesn’t matter much, you can probably just keep going and see if any errors come up.
As a special test beyond the usual, a somewhat technical approach would be to install DB Browser for SQLite, shut down Duplicati, open a copy of your database and run SQL PRAGMA integrity_check
Database disk image is malformed gives an example of this test, but don’t go right off trying to repair it