Ranked > Inactive

I completed my placement games and achieved my rank, however I haven't played ranked since. If I become "inactive" for not playing more ranked games how will that effect my current placement and will I be "demoted" to a lower rank and lose the rewards before the season ends? This is my first season playing LoL so I'm unfamiliar with how it works and can't find any discussions relating to my questions. Thank you. TheBride