What is the usual ban time for a soft ban for violating the 1 second rule?

Forever ;)

While that's not true (but should be), see https://operations.osmfoundation.org/policies/nominatim/

But for any serious business you should either setup your own nominatim instance or use one of the providers or services listed here, here or here.

The nominatim instances run by OpenStreetMap are run by volunteers on donated hardware and may get overloaded or may stop serving you anytime and are not recommended to be used for a regular business endeavor.