Daily drivers don't need brake fluid replacement at 30K miles. Performance car maybe. But some people change their engine oil way too early based off of "feelings" too so yeah do what you want if you don't care about science and facts. LOL

 

Never changed break fluids on following cars in the family.
Never even topped it off. Level goes down as pads wear out, after pads replacement level goes back to normal

Camry 160K miles over 10 years
RX 330 130K miles over 10 years
Acura TL 160K mile over 12 years

Maybe if you are riding mountain road when you are boiling your fluid, otherwise it doesn't even change color.

 

To keep your warranty intact you have to follow the maintenance schedule that Lexus provides. Once out of warranty, you are free to do whatever your heart desires.