How long after my acne is gone should I still take my oral meds for it? Doxycycline 100mg 2x a day?

I use a salicylic wash 2x day, retin-a as needed and benzoyl peroxide cream in the morning. I also do an exfoliating mask 2x week or less. I am going off health ins. and my skin has been very clear for the past few months. I really dont want to continue taking oral meds and have enough of the creams to use for another year or so. Is it good to take doxycyclin 100mg 2x day for over 6mo? If I go off of the oral pills, will I get acne again? Are there any healthier alt. to this prescription, perhaps vitamins over the counter?? I've never had severe acne, just light adult acne,but i can tend to get smaller scars after a big breakout but I havent had one in a very long time and my skin has been very clear.