How does a God that always was, just die at a certain point, or a God that has a begining but always was, make sense. Aren't they botha little contradictory? I may be overcomplicating the problem, but that is how I see it.
For one thing, I never mentioned a god, I was merely responding to the claim that something that has always existed
must always continue to exist.
To your points, though, why couldn't a God have a lifetime of 15 billion years? Since the Universe is just under 14 billion years old, that god would have existed forever, as far as this Universe is concerned, and could die at any time in the next billion years.
Similarly, the half-life of a proton is expected to be longer than the Universe has currently been in existence, but that doesn't mean a proton won't ever "die."
As for your second point, either you misread what I said, or misstated what you mean. A god that has a beginning, but always was, makes no sense. A god that never dies, but begins at some point in time, does...sort of. Let's go with the new big movie coming out, X-Men Origins: Wolverine. Let's say we come up with a syrum, or we develop a mutation, that grants immortality, much like Wolverine has. Theoretically, Wolverine will never die, but that doesn't mean he has always existed, does it?