I think the NFL formula for sustainability at a very high level is a great GM who can identify NFL talent in later rounds.
That's the pipeline to move a backup into a starter position without losing talent level and... not succumbing to Salary Cap Hell.
Also, depth players on a high level team are critical so, even if a later round guy never becomes a starter and is nothing more than a depth guy... that ALSO plays a role in the above...
This is the most encouraging thing I see in Holmes, and why he was hired: The ability to identify NFL talent in any round. Whether that's a depth guy, special teamer, or sneaky future starter...
We'll see how good he is at this, or not, over the longer term 4-5-6+ years...