I saw a bra fitting thread wondering if it was worth the time, so of course I had to get on my soapbox. This is my first post in the forums, imagine that! LOL.
As someone who is a certified bra fitter by trade I say yes it is absolutely essential to get fitted when buying bras. The life of a bra is only 3-6 months depending on how many you have and how often you are rotating them! Generally you should have four. One on your body, two in the drawer, one in the wash, and rotate. After that period of time the elasticity gives out and it's not doing anything for you other than just making a pretty (and in most cases expensive) boobie cover.
Really you should get fit every time you buy bras because as your weight fluctuates, so will your bra size. A loss of ten pounds or so can change and entire cup size in most cases. The band size goes a little slower because the weight around is harder to lose.
YOUR BAND GIVES YOU 90% OF YOUR SUPPORT LADIES SO DONT WEAR IT TOO BIG. When most women try on bras and they fit tightly, the first thing they do is go for a bigger band. PLEASE STOP!!! Instead go up a cup. A bigger cup gives you a little more wiggle room in the band so don't worry! If your band is too big, you are getting no support. You should be able to run two fingers underneath the band without it shifting. It is supposed to be snug.
Bra's are made for utility, not comfort. They are made to distribute the weight of your breasts evenly so that it is less of a burden on your back. You will feel it for awhile, I'm sorry those of you who want to feel like your bra doesnt exist! You should really go as small as possible in the band to get the maximum support without it restricting oxygen or anything vital
Make sure your fitter is experienced. This is probably the most important part of your shopping experience. And please trust her. Even if you dont believe the size she tells you, be open to it and try one on. Whats it going to hurt? Your fitter should be measuring you in two places: underneath the bust to get your band size, and around the fullest part of breasts to get the cup. If they simply measure you in one place and spit out a size they most likely do NOT know what they are doing (Victorias Secret is infamous for this). Also keep in mind that if your fitter fits you as a 38DD and the first bra you try on in that size doesnt work, doesnt mean she doesnt know what she's doing! Different style bras run differently in sizes. That is why you MUST TRY EVERY BRA ON! It's all about trial and error.
So happy bra shopping ladies! A properly fitted bra can make you look ten pounds thinner so it is definitely worth the time!
I also wanted to add that you should be hooking your bra's closed and washing them on delicate inside of a lingerie bag (hand washing is actually preferable but who has time for that?!). No bra's in the dryer for that is the biggest sin of all. Lot's of great bra's have been lost to them. Simply wash and lay flat to dry. You'll add months onto the life of your bra (but no bra should be more than six months old. seven tops!).