Some people have perpetual die-off because they feed the candida treats like rice, corn, fruit, potatoes, carrots, etc. and could have SIBO or a different infection. Everyone is different. Generally speaking it should last under 1-2 months if you kill it quickly.
You won’t be able to eradicate the infestation completely because you need candida to live; if you didn’t have candida you would die. The goal should be to reverse the candida back to its non-pathogenic form which is mostly harmless. You should know when you feel “better” pretty easily though…you should feel like you did 5, 10 years ago.