So, you would feel sensible in caring about (having altruistic feelings for) someone who could remember being you. Yes?
Would you feel sensible in caring about the future-you if (the present) you knew that he was going to have amnesia?
Me: "I'm going to drain my bank account and run wild, having a good time, because I know that tomorrow (and forever after) I won't remember having done such a dastardly thing to myself."
It's not about what _I_ feel sensible about caring about. We're talking about a hypothetical individual who cares only about versions of himself that share a common ancestor or descendant state.
If such an individual were given advanced knowledge of an irreversable amnesia, then logically he would commit acts that benefit him and cost the individual inhabiting his body in a day's time. So yes, it makes perfect sense.
But given the same circumstances, I'd behave differently, as I'm not a sociopath.
Would you feel sensible in caring about the future-you if (the present) you knew that he was going to have amnesia?
Me: "I'm going to drain my bank account and run wild, having a good time, because I know that tomorrow (and forever after) I won't remember having done such a dastardly thing to myself."
Does that make sense?