Actual resistors is fine for your use, so long as the resistors mount inside the air duct, so they get good airflow. This is required to cool the resistors.
The resistor design is probably cheaper to produce, which is why they sell it.
If it ever stops working in the future, it's probably the thermal fuse that has let go, and not the entire resistor pack. The thermal fuse sits next to the resistors itself; new ones are usually available at Radio Shack.