I don't think lying has much of an effect, the main thing that counts for "potential future" is being alive / able to "live". IIRC the metric is routinely used

I don't think lying has much of an effect, the main thing that counts for "potential future" is being alive / able to "live". IIRC the metric is routinely used when evaluating new treatments, measuring their associated cost in $/DALY helps comparing and price negotiations. If things are really tight (think war, poverty, pandemic, etc) I think at least it can be fair and effective. One can't live forever, and IMHO prioritizing younger people for medical care is widely accepted. Of course there needs to be a few humans in the loop as it's just a statistic and there are no guarantees. And obviously a cold soulless robot AI optimizing for it would be insane, but that goes for most metrics.