Hydraulic disc brakes are the best performing brakes you can possible find.  They do require regular service to continue to perform.  If you do not bleed the system regularly, the seals will deteriorate and the brakes will need to be overhauled or even replaced within a few years.

Brake bleed intervals should be no more than 2 years apart.  The frequency depends on the type of brake fluid that is used in the system, either DOT fluid or mineral oil.  DOT fluid needs to changed more often (once a year) because is absorbs moisture quicker than mineral oil.  Mineral oil systems should be bled every other year.  Hayes, AVID, Formula, and Hope all use some form of DOT fluid.  Shimano, Magura and Tektro are all mineral oil based systems.

Fitness Central is fully equipped to bleed and service any system you have.