Perennial typically describes things that are permanent, constant, or repeated. If you fight with your parents every year over whether they really must invite your annoying cousins for Thanksgiving, you could call that a perennial conflict.
Arguing with your roommate about who cleaned the bathroom last time might be a perennial argument. There is also a perennial plant, which lasts more than two years and usually reappears each spring, because it produces flowers and seeds from the same root structure. Perennial comes from the Latin perennis, from the prefix per-, "through," plus annus, or "year." Annus is also the source of our English word annual — an annual plant lives only one year or season.
adj lasting an indefinitely long time; suggesting self-renewal
primarily temporal sense; being or indicating a relatively great or greater than average duration or passage of time or a duration as specified