iPhone app under test crashes after a few days

Solution 1:

If application is installed with Xcode and you don't have a Paid Program Developer Account, the life expectancy of the app is approximately 48 hours (There is no official time of validity for this).

For a paid program, it's a few months with the correct certificate. With TestFlight, it's now 60 days.

Indeed, if you don't sign your app, it has low life expectancy. It's quite new that Apple allows installation to devices for free accounts, but it's just for testing purposes (other than simulator), if you want more days to test on a device, you have to pay for the developer program.

Solution 2:

No it's not a guess actually...

It's 7 days exactly for a free developer account.

You can check validity also in Xcode Provisioning profile also:

In General → Signing ("Automatically Manage Signing" checked) → Provisioning Profile (Click on Info (i) icon) you can check validity of the profile: