  Caches in Content-Centric Networks (CCN) are increasingly adopting flash
memory based storage. The current flash cache technology stores all files with
the largest possible expiry date, i.e. the files are written in the memory so
that they are retained for as long as possible. This, however, does not
leverage the CCN data characteristics where content is typically short-lived
and has a distinct popularity profile. Writing files in a cache using the
longest retention time damages the memory device thus reducing its lifetime.
However, writing using a small retention time can increase the content
retrieval delay, since, at the time a file is requested, the file may already
have been expired from the memory. This motivates us to consider a joint
optimization wherein we obtain optimal policies for jointly minimizing the
content retrieval delay (which is a network-centric objective) and the flash
damage (which is a device-centric objective). Caching decisions now not only
involve what to cache but also for how long to cache each file. We design
provably optimal policies and numerically compare them against prior policies.
