<div>A decision-maker periodically acquires information about a changing state, controlling both the timing and content of updates. I characterize optimal policies using a decomposition of the dynamic problem into optimal stopping and static information acquisition problems. Eventually, information acquisition either stops or follows a simple cycle, with updates occurring at regular intervals and leading to consistent certainty levels. In the limit as costs vanish it is optimal to trade-off quality for frequency; surprisingly, this entails that both belief and action changes become lumpier. By contrast, the optimal frequency of information acquisition is generally non-monotonic in the volatility of the underlying environment. I study applications to investment problems, highlighting consequences for portfolio diversification and asymmetries between safe and risky assets.</div>