In the Culture novels, he has all humans just sorta choosing to die after a millennium of life, despite there being absolutely no reason for humans to die since available resources are unlimited, almost all other problems solved, aging irrelevant, and clear upgrade paths available (like growing into a Mind).
Its not entirely clear cut. He has had characters from outside the culture describing it as a 'fashion' and a sign of the culture's decadence. And the characters we do see ending their lives are generally doing it for reasons of psychological trauma.
Either way, thinking a thousand years in the culture is enough doesn't mean he thinks 70 years on earth is enough. Has he ever made a direct comment about cryonics? I can't find any. So its still possible eh would eb open to it given up to date information.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.