iPhone app under test crashes after a few days
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.
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:
This forum helped me find an answer for a very similar issue I was facing with an Ionic iOS app I have running on a few iPads for a checkin kiosk at a non-profit I am developing for. For my scenario I just need the apps to run locally on WiFi and never on any other devices, never to be downloaded as a distributed app to the public. My apps kept randomly crashing on launch, and I would re-install the app from Xcode and they would start working again.
So my only real solution was creating an "Ad-Hoc" certificate and provisioning profile, where you can add up to 100 iOS devices to the provision. I had to manually add my 3 iPads to the provisioning profile, then download the file and open it, then in Xcode un-check "Automatically manage signing", then go below to "Provisioning Profile", then select your new ad-hoc style profile. And you should be good as long as your Apple developer account is in good standing (I believe, someone correct me if I'm wrong).
Just a heads up, first you personally have to be a paid and registered developer with Apple, not just added to a team by invite. I was invited in by another team for a completely different project and was not able to get set up and create the certificate and provisioning file on my own because of that. I had to leave my team, then register anew with Apple as an individual developer, then I could complete my steps.