This paper shows that versions of prioritarianism that focus at least partially on well-being levels at certain times conflict with conventional views of prudential value and prudential rationality. So-called timeslice prioritarianism, and pluralist views that ascribe importance to timeslices, hold that a benefit matters more, the worse off the beneficiary is at the time of receiving it. We show that views that evaluate outcomes in accordance with this idea entail that an agent who delays gratification makes an outcome worse, even (...) if it is better for the agent and worse for no one else. We take this to show that timeslice prioritarianism and some pluralist views violate Weak Pareto, and we argue that these versions of prioritarianism are implausible. (shrink)