Last year Google introduced a developer preview for the release of the L version of Android, which went on to become Lollipop. There was very little in the way of updates, with the preview software displaying some showstopper bugs throughout their lifecycle. Google has learned from this and has advised in their developer documentation that the Android M preview will not suffer the same fate, with monthly updates planned.
Not only will the updates come monthly, you won’t even have to flash the images again, with the updates coming as Over The Air updates. The doco clearly states below the image download links :
Android Police further confirmed the monthly update cycle, with Dave Burke, VP Engineering (Android) at Google.
If you haven’t yet, check out our guide on how to flash the developer preview to your Nexus 5, 6, 9, or if you’re not quite that adventurous, check out the Quick Look at the Android M developer preview.