  I consider the sequential implementation of a target information structure. I
characterize the set of decision time distributions induced by all signal
processes that satisfy a per-period learning capacity constraint. I find that
all decision time distributions have the same expectation, and the maximal and
minimal elements by mean-preserving spread order are deterministic distribution
and exponential distribution. The result implies that when time preference is
risk loving (e.g. standard or hyperbolic discounting), Poisson signal is
optimal since it induces the most risky exponential decision time distribution.
When time preference is risk neutral (e.g. constant delay cost), all signal
processes are equally optimal.
