[tboyd47]

You need at least 2 sandbox environments: one that's more development-oriented (little to no restrictions on merging), and one that's more release-oriented (as close as possible to production).

Ideally you have 3, and the third one is not used except to demo new features to customers AFTER they have been released (and perhaps, hidden behind a feature flag).

If you only have one sandbox, then it becomes a brawl between development, sales, and management.

More than three is overdoing it and assuming a technical burden for no benefit. (No, you don't need the capacity to spin up sandboxes willy-nilly. Three is enough.)