  Age of Information (AoI) is a key metric to understand data freshness in
Internet of Things (IoT) devices. In this paper we analyse an
intermittently-powered IoT sensor - with mixed-memory (volatile and
non-volatile) architecture - that uses a Time-Dependent Checkpointing (TDC)
scheme. We derive the average Peak Age of Information (PAoI) and average AoI of
the system, and use these metrics to understand which device parameters most
significantly influence performance. We go on to consider how the average PAoI
of a mixed-memory system compares with entirely volatile or entirely
non-volatile architecture, and also introduce an alternative TDC strategy to
improve system resilience in unpredictable environmental conditions.
