There is no right answer to this question, there could be a release every ten minutes, every hour or once a week. It all depends on the EXTENT of automation you have at a different level of the software development lifecycle - build automation, test automation, deployment automation and monitoring. And of course on the business requirements - how small low-risk changes you care making in a single release.

In an IDEAL world where boundaries of each microservices are clearly defined (bounded context), and a given service is not affecting other microservices, you can easily achieve multiple deployments a DAY without major complexity.

Examples of deployment/release frequency

1. Amazon is on record as making changes to production every 11.6 seconds on average in May of 2011.
2. Github is well known for its aggressive engineering practices, deploying code into production on an average 60 times a day.
3. Facebook releases to production twice a day.
4. Many Google services see releases multiple times a week, and almost everything in Google is DEVELOPED on mainline.
5. Etsy Deploys More Than 50 Times a Day.