It really depends. I got mine about a week ago, and have worn it less than 8 hours a day for 4 days (I worry about the injuries I have read occurred when worn for long durations). It took about two of those days for me to break in a Double Panel Compression Shirt Binder from Underworks that I got for my double D's. It just depends on where you got it, what you got, duration of wear, and sizing (if you got a size smaller for better compression or your regular size). I hope this helps.