is it posible to make flexibility permanently?

hello guys , first of all sorry for my lack of english , i got a question over here,



is it possible to make flexibility permanently , i mean not lose it even if you stop stretching.



when i was a kid like 4 -6 years old i stretched the butterfly type which is that







my both legs hit to the ground and i can even bite my bigtoe when i shut myself to the floor , i didnt even stretch since 15 years and i didnt lose my butterfly flexibility ( i think its cause i was a child when i stretched ) , but i cant side split or other stretchings , i am doing taekwondo for 10 months and stretching 3 days in a week , is it possible to make the other stretch types permanent like my butterfly stretch if i keep stretching to the limit since i am a 21 years old adult anymore