This questions is really answered best by your own plastic surgeon. Some prefer bras for a few months, others do not feel it matters at all. For your specific case, simply give a call to the surgeons office. I prefer to keep my patients in a bra for the first 6 weeks after breast augmentation.
I see no reason why you can't go without a bra.I would not do it 24/7.this will only cause your breatss to sag more so support is important.