Migraine headaches which occur on 15 or more days of the month for 3 or more months without a medication overuse are regarded as chronic migraines. Most affected people with chronic migraine had migraine without aura before. Apparently, chronification can be seen as a complication of an episodic migraine. During a chronification the headache has the tendency to loose its episodic course but not in every case.
In pain terminology chronic means a persistence over a time period of at least 3 month. In headache terminology this meaning is kept for secondary headache disorders. For primary headache disorders, which often occur periodically, the term chronic is used when the attacks occur on half of the days for at least 3 months. Trigemino autonomous headache disorders are an execption. It is a chronic progression only if the disorder did not subside for over one year.
Daily use of triptans is no appropriate solution even for chronic migraine. An effective prophylaxis has to be found. Additional illnesses also need to be treated specifically. That is the only way to arrive at a more stable situation.
Chronic migraine can be very aggressive for many years and refuse treatment. However, for exactly that reason you should specifically search for other ways of treatment with prospect of success and not give up. That actually can take years sometimes.