I am pro-immortality, but the above isn’t entirely valid. It’s possible not to know the optimal human lifespan, while still believing, for instance, that 500 years is too much.
I think this is a good point but I think my argument still applies: Brin and PZ should provide a range, which could be rough, (perhaps an order of magnitude as jaibot suggests) and defend it. This would force them to look at the pros and cons and estimate them. Or admit that such things are extremely difficult to estimate. Arguably a serious analysis of this issue requires no less.
I think this is a good point but I think my argument still applies: Brin and PZ should provide a range, which could be rough, (perhaps an order of magnitude as jaibot suggests) and defend it. This would force them to look at the pros and cons and estimate them. Or admit that such things are extremely difficult to estimate. Arguably a serious analysis of this issue requires no less.