How could long term fioricet / fiorinal (aspirin butalbital and caffeine) users or abusers affect someone?

Many Ways: Aside from the likely liver or kidney damage from the Aspirin or tylenol (acetaminophen) contained in these combinations, assuming that you were taking the meds for headache, you will probably develop medication overuse headache. There is also the possibility of developing a barbiturate dependence which could lead to seizures if you stopped the drug suddenly.