If you're just taking one a month: no, they wouldn't be addictive. But benzodiazepines are misused as streetdrugs frequently, and if people build up tolerances and take more than they should they can be highly dangerous.
Example: Clorazepam at 4mg can put you to sleep but is also likely to make you stop breathing, and you could die. I did this without knowing and shocked my psychiatrist. I build up tolerances so quickly to medications so benzodiazepines aren't for me.