Windows Phone 8 apps needs to be beta tested for bugs and inclusion of additional features as suggested by users. Michael Crump, Software Developer and Microsoft MVP has been working with Windows Phone 8 apps for the last several months and provides answers to few hidden questions based on his experience.
Windows Phone 8 Beta Apps will expire after 90 days of successful submission. You can check the submission date by clicking on apps and then selecting your relevant beta app. Once expired, you can no longer run it on your phone. However, it is possible to send feedback and uninstall the app at any time.
You should also note that your beta app does not count against your submission credit. Moreover, if the developer unpublishes the app from the dev center then new users will not be able to install it. However, those users who have installed the app previosuly should remove it either manually or wait until it expires.
Microsoft policies doesn't allow you to set a price for a beta app during the submission time and a valid Microsoft account (formerly formerly Windows Live ID) is required to beta test an app. Moreover, developers will have an ability to beta test in-app purchases and only those people who have been flagged as beta testers will receive a link to download the app.
As a developer, you can't extend the life of a published beta app. You have to resubmit the app as another beta upon expiry of the original version. However, it is possible to update an app in beta stage without starting the whole process from the beginning.
Post your questions regarding Windows Phone 8 Beta Apps and InfoQ will try to get in touch with Michael to answer them.