2003 Honda Accord Brake Fluid

Hi There, my owner's manual maintenance schedule shows that I need to replace brake fluid every three years (independent of mileage) but the service manger at the local repair shop ( Not the Honda Dealership) that I go to says I do not have to replace brake fluid ever. He says it is a closed system and fluid does not deteriorate. I don't even remember when was the last time I replaced brake fluid, now my car is 7 years old and has 90K miles. Can you please tell whether replacing brake fluid is needed or not. Pros and cons of replacing or not replacing it. Also if you can tell how much it usually costs to replace brake fluid, I will appreciate it. Thank you in advance.