title: EXPIRE Redis key if not modified
body: <p>Is there a straightforward way to EXPIRE a redis key if the value has not been modified in the last x minutes?</p>
  
  <p>I doubt this is possible - but I am wondering if there is native solution or something with very little logic and/or extra state.</p>
  
  <p>Now, this behavior might already be present - I invoke EXPIRE on a key. Then if I call SET on that key I can call EXPIRE again and the key will EXPIRE with the new value not the old?</p>