Oral B Sonic Brush Heads

I recently started using the toothbrush Oral-B Sonic, but do not know how long before I should buy replacement brushes for the handle. Suggestions?
Thank you very much!

I replace mine every three months, as you would a regular toothbrush

6 months is the usual period

After 6 months should do it.

when the bristles are bent and crushed by all-but prolly every 3 months or so

i replace mine every 4 months

well if u brush is old may obtain one by all means we can uu until it gets old.