Although most don't know it, app updates are one of the best marketing tools app developers have at their disposal. With the number of apps people have installed on their devices today, regular updates can help an app get more mindshare relative to other apps on a device. Releasing regular updates keeps an app top of mind because it will show up in the updates list like the App Store or Google Play Store. Apple and Google also like to see app updates, especially with their major OS releases, which is why we recommend to have your app updated on major OS launch days.
App updates can also help build a loyal following, provided that the updates include relevant bug fixes and features that users are requesting. Frequent updates show you're committed to the app and that it's still being maintained. Having a loyal following for your app will help it spread on and offline. The most loyal users may even suggest your app as an option when people ask about alternatives to apps they are using now. This type of commitment could never be earned just through marketing alone.
Finally, app updates offer a way for a developer to speak with their userbase via release notes. While a smaller number of users likely will read the release notes, the ones who do are often the most technically savvy and engaged. Release notes should definitely not be overlooked.
While the number of app updates will generally be in the range of 1-4 per month, obviously where you fall on the spectrum will vary. Individuals or smaller teams may only be able to get out a quality release per month. Larger ones with more mature apps will usually be in that two, three, or even four updates range. Continue to balance adding features and stabilizing your app. Stay disciplined and avoid app scope creep. With this approach, you'll ultimately put yourself in the best position to have a healthy set of updates flowing to your userbase.