"this old" according to what clock? What if the refresh fails or times out? Do you keep the old value there until a refresh succeeds?
etc, etc, etc.
Even that simple example is not remotely easy if "if it's at least this old, refresh it" is an actual requirement. Thankfully most of the time it's not, and the requirement is actually "refresh it every once in a while, about this often, but none of this is particularly important so it doesn't have to always work"
etc, etc, etc.
Even that simple example is not remotely easy if "if it's at least this old, refresh it" is an actual requirement. Thankfully most of the time it's not, and the requirement is actually "refresh it every once in a while, about this often, but none of this is particularly important so it doesn't have to always work"