"unsustainable" can last a very long time ...
I'm reminded that an unsustainable trend can last 100 million years, as in the case of the Oxygen Catastrophe (2 billion years ago).
The Sun is about halfway through its natural lifespan, it has another 5 billion years to go, but the Earth will become uninhabitable in about 1 billion years as the Sun continues heating up (regardless of greenhouse gas emissions on Earth).
In the case of the ongoing expansion/inflation of the known universe, there will no longer be enough fuel for stars to form after another 50 trillion years.
The Sun is about halfway through its natural lifespan, it has another 5 billion years to go, but the Earth will become uninhabitable in about 1 billion years as the Sun continues heating up (regardless of greenhouse gas emissions on Earth).
In the case of the ongoing expansion/inflation of the known universe, there will no longer be enough fuel for stars to form after another 50 trillion years.