This lady in a department store said that I should be refitted for a bra every six months whether my weight has changed or not. Is this true? I have never heard of that. Even, if my bra still fits, I need to be refitted?
I think once a year is fine and you can measure yourself, no need to go to a store. Most stores use outdated measuring methods anyways and will give you a wrong size. Here's how to measure yourself using modern standards.
Band = underbust measurement rounded up to the nearest even number (directly underneath where your tissue stops under the breast) Cup = bust (fullest part around your breasts) - underbust
I measure 29 and 37. My 29 underbust with the 8 inch difference make me a 30FF. IF you think that's big look again: http://imgur.com/a/m71Li
If you don't want to be refitted, don't do it. I still prefer it (better safe than sorry) but it's so quick and easy that it doesn't bother me. If you try on the bra though, you'll know if it fits regardless as size so it's really not necessary.