How long to receive soft bounce email reply

From this AWS blog post:

When a soft bounce event happens, SES continuously retries to deliver your email for 12 hours before giving up. There is no limit of retries during this 12-hour interval, and, as long as the ISP recovers, your email will be delivered.

From the SES documentation, soft bounces ("Transient") can occur for a variety of reasons. It is recommended that you monitor your bounces and take action based on the bounce types by analyzing the bounceType and bounceSubType fields.