If you're easily offended, please don't read any further!
Do yourself a favor and choose a date every year to go out and buy a new bra. Whether it be your birthday, your anniversary, some other special date or one you just pick out of the air ~ mark your calendar and go shopping on this date.
Get fitted for the correct size and buy at least 2 bras that you can alternate throughout the year. DO NOT keep your old one "just in case" you need it some day; you won't. Once you put on that new bra, you'll never wear your old one again... it'll just sit in your dresser taking up valuable real estate.
I had noticed that I was adjusting the straps of my old one constantly throughout the day; this is the first sign that your bra has worn out. I bought 2 new bras last weekend for $20 each at Kohl's... that's not a lot of investment for a year's worth of comfort ladies!
Today, the "girls" are sitting higher, my posture has improved and most of all, I feel prettier. Isn't that reason enough?
Go shopping... you deserve it.