It is a sin, according to Nordstrom where I buy bras. They say that to prolong the life and shape of your bra, you should alternate it with other bras. I have three bras and make sure each of them gets at least a day's worth of rest. I then go buy new ones every 6 months. With all the weight gain, Zyprexa and other stuff, I measure 42 DDD. I started being smaller than 32D. Apparently larger breasted women need to change their bras every 6 months and smaller breasted, every 9 months. But that is with owning 2-3 bras total. If you have 7 or more, you would be wearing each so infrequently (unless you repeat one day in and day out) that they will last for much longer. That said, weight gain makes one change in size, so a trip to a fitter is still a good idea. The last bit of bra virtue so that you would not sin - start wearing a new bra on the loosest hooks and later, as the bra gets stretched, move to tighter hooks. Sin no more, I say!