What is the time spand inbetween each time i bleach my hair?

i want to get my hair from dark brown to blonde. i have bleached it twice already to get it almost blonde. i want to bleach it one final time to get it to the perfect blonde color i want it. Is it safe to bleach it again? The last time i bleached it was 2 weeks ago. I dont have to leave it in long because it is so close to the color i want.