If you plan to keep the bike for 30 years, flush and bleed the system on a regular basis, perhaps every 2 years. If the bike is a disposable unit, one that you will get bored with in 10 years just let it go and pass it on to the next owner.
Just like an automobile the brake fluid is not only used for compression it is used as a lubricant within the system. Fresh lube keeps things working well for a very long time. I have a 40 year old Volvo that gets regular fluid flush and bleed and still using the original calipers and master cylinder. The bicycle is no different.