Apps Made In Unity Wont Stay On iPhone

I create Virtual Reality scenes in Unity from within Windows, for use on my iPhone 6 running iOS 10.2, and using GoogleVR SDK for Cardboard devices.

I create a project, and save to iOS format.

I run macOS 10.12 in a virtual VMware environment in Windows.

Inside macOS 10.12 I use Xcode 8.2.1 to, "sideload" my Unity project, onto my iPhone.

It works, dont get me wrong.

But the problem is this:

After about 2 or so days of my Unity App being on my iPhone, the icon for my Unity App remains, but now if I try to run it, I tap the icon, screen drops to black for a second, and then simply comes back to the screen with the icons.

The App works great, but only for about a day or two, and then, the above happens.

Why does my App only run for a certain amount of time on my iPhone?