It depends on your Jeep's design and the motor's condition. On models where the regulator and motor are sold as a single combined assembly, the motor gets replaced along with the regulator regardless of its condition. On models with separate parts, replacing just the regulator while keeping the motor healthy is usually fine. However, a motor that's already showing signs of weakness is worth replacing at the same time.
Many newer Jeep models use a regulator and motor built into a single riveted or bolted assembly, which means there's no practical way to replace only the regulator, even if the motor itself is working perfectly. In these cases, the parts design determines the decision, and the labor to access the door usually stays the same either way, so replacing the combined unit doesn't add much extra cost.
On older Jeeps and models where the motor and regulator are separate, it makes more sense to evaluate the motor on its own. A motor that's still running the window at a normal speed with a steady sound, and wasn't itself the cause of the failure, can usually be reused without issue, since motors and regulators don't typically wear out on the same schedule. Reusing a good motor keeps the repair cost lower without sacrificing reliability.
It's worth reconsidering when the motor is already showing early warning signs, like a window that moves more slowly than it used to, a slight hesitation before it starts moving, or a faint grinding sound. Since the door has to be opened up anyway to replace the regulator, and the labor to access both parts overlaps almost entirely, this is often the most cost-effective time to replace a tired motor before it fails on its own a few months later.
If you're not sure whether your Jeep's motor and regulator are separate parts or a combined assembly, or whether your motor is worth reusing, Hoover Street Auto Repair in Ann Arbor can inspect both and recommend the option that makes the most sense for your specific Jeep.