Bras stretch over time. They are not meant to last a lifetime. You will have to bid goodbye to your favorite bras after a certain point of time when it gets loosened. They last for 3–6 months time. Once it gets loosened, it will not support and lift your bust any longer. Many women tend to wear bras for years which is why they tend to loser the firmness of the breasts.
Bras never shrink but only stretches. One need to carefully take care of bras before and after it gets washed. You need to give a one day break before you wear it again so that it gets back to its shape again.