There’s a crude inductive argument that the future will always outweigh the present, in which case we could end up like Aesop’s miser, always saving for the future until eventually we die.
I would just note that, if this happens, we’ve done longtermism very badly. Remember longtermism is (usually) motivated by maximising expected undiscounted welfare over the rest of time.
Right now, longtermists think they are improving the far future in expectation. When we actually get to this far future it should (in expectation) be better than it otherwise would have been if we hadn’t done what we’re doing now i.e. reducing existential risk. So yes longtermists may always think about the future rather than the present (until the future is no longer vast in expectation), but that doesn’t mean we will never reap the gains of having done so.
I would just note that, if this happens, we’ve done longtermism very badly. Remember longtermism is (usually) motivated by maximising expected undiscounted welfare over the rest of time.
Right now, longtermists think they are improving the far future in expectation. When we actually get to this far future it should (in expectation) be better than it otherwise would have been if we hadn’t done what we’re doing now i.e. reducing existential risk. So yes longtermists may always think about the future rather than the present (until the future is no longer vast in expectation), but that doesn’t mean we will never reap the gains of having done so.
EDIT: I may have misunderstood your point here
Yeah, this wasn’t my strongest/most serious argument here. See my response to @Lukas_Gloor.