A common issue on the DC17 model is the suction disappearing, and eventually the motor turning off. The issue is likely a very easy fix. A lot of people have gotten rid of their Dyson altogether when they could have solved the problem in less than a minute.
The likely reason your DC17 has lost its suction is because the seal at the bottome of the cyclone assembly is not as tight as it needs to be, so over time, if the bottom of the bin is not closed precisely each time, it will push up on the rubber seal, and little by little over time, push it up.
The solution is simple, just open up the bottom of the bin and pull the seal back into place all the way around (yes, you will have to wash your hands when you are done).