Only use toast to reinforce updates
Toast snackbars should only be used for non-critical messaging, and the status described should be discernable on the page.
For example, upon changing state of a toggle to unsubscribe from a list, the toast can reinforce the change has been saved, but the user can also confirm this from the toggle itself.
Do not use toast for critical functionality
Never use toast for critical tasks (Ex: undo/unsend or confirmation of choices).
It is preferable to not let a toast snackbar time out.