I have ridden hydraulic disc brakes for five years and have two or more years on four bikes equipped with them. Over 100,000 miles. I bled the brakes meticulously (obsessively) when I installed them. I have never, ever had to re-bleed or replace the fluid on any Shimano hydraulic disc brake. They work exactly the same years later as they do on the day I install them.
If the initial installation is done meticulously (obsessively), there's no reason to have to maintain anything other than pads and discs as they wear out. If it was installed well, keep the hydraulic system sealed and it will be your friend for a very long time.