It has been confirmed by Google that most Google Posts are removed seven days after they’re first published. The only exception to the rule is Google Posts that are based on any upcoming events Once the event day comes and goes, that event-based Google Post is removed.
According to a Google spokesperson, “Posts enable merchants to share timely, relevant updates on Google Search and Maps. To ensure that posts are timely, they’re removed from the default view after seven days (or when the event date the post referenced has passed). However, a historical view of posts is shown under the Posts tab on mobile.”
Recently, Google Posts went live to most Google My Business customers, allowing businesses to share timely messages to their customers. These posts will show up in the local panel on both web search and Google Maps.
Brodie Clark from optimising.com.au shared a screen shot of a Google notification that notifies businesses that the Google Post is going to expire: