depends on what you use them for. if you look at the specs, the motor in the harbor freight 4 1/2" angle grinder is a lot less than that of a DeWalt or name brand more expensive grinder. The harbor freight grinder will last a long time if you realize the motor is not as big.

We keep an assortment of grinders at the shop including the harbor frieght cheapos and some more expensive dewalts. The harbor freight ones work good for basic grinding and light duty cutting. But if i'm going to a lot of hard grinding on say a bumper or some long cuts of 1/4" plate, i'm reaching for the DeWalt.

If you don't heat up the harbor freight grinder, it will last a long time (i've had some going on years). and at $20 a pop, big deal if you throw one away a year under heavy use... basically use as a disposable grinder.

-Rob