So, I bought a new bike back in November with SRAM Force groupset. It’s my first time owning disc breaks.

By March I had no breaking power at all on the rear and much gone on front. Took the bike to redbeard. Two weeks later I found less braking power in rear, so I took it back to redbeard where they heard a burping sound, so they changed the rear system in guarantee.

So my bike has done ok, though spent a lot of time in the trainer, and now the breaks are reaching the drop bars again. 

Is this normal? How often should disc breaks be bled? Is there something I could be doing wrong that is causing this? I’m bringing my bike again at redbeard for full service on Tuesday, is there anything in your experience that could be causing this (so I can mention it to them)?