Question: how long should it take to get a black belt in taekwondo?
Answer: In Taekwondo, it is likely that a dedicated student will be eligible to test for a 1st Degree Black Belt (Il Dan) after 3 to 5 years (at my Dojang, the minimum time is 4 years). Students can fail a Taekwondo test, and I have seen it happen many times over my decades in this art.