I definitely fear for this issue. Not just in underwear, but clothes in general. My current size is 34E and while some of my E cups are getting loose, others are not. Weird, I know. Like yourself, I don't have the money to be going around and buying new things every couple of weeks but I wouldn't mind spending a couple of euros to go and get a new bra when I need too. The best advice would be to go cheaper and use the cheapie ones for a while until you reach your goal weight which you know you will maintain then you can go back to getting a couple of better quality ones. Once mine do become too big for me, I know I won't be able to get away with going around in one. So I'll just settle for the cheap ones until I reach my goal.