Old Smokey,
The notion that someone has a handle on their addiction if they can abstain for a short period of time is not founded on any scientific basis and is a tactic often deployed by people with dependency problems.
Diazepam is not good for solving sleeping problems and has in common with all other benzodiazepines that they are highly addictive, both psychological and physical.
Zopiclone is better but by no means non-addictive either.
These drugs were initially hailed as being brilliant but as so often when used in the general population proved to have addictive propensities too.
People best check any medication they take against what is allowed by their regulatory authority. All Benzos are forbidden by the FAA.