Just in case, I put spoilers in the subject line just in case anyone still hasn't read it yet.
Do you think Superman just survived an alien planet's destruction or not? I ask because that is exactly what it looks like to me.
If Superman was able to save a single life, he would stay until that life was saved. Until he was absolutely sure. Therefore he was still there when the planet started to explode, and it was only when there was no one left to save that he turned and flew away.
So, yes. It was a durability feat.
Our boy is back!