There isn’t a universal rule. Shutter life depends heavily on the specific shutter design, materials, and camera class being compared.

In general, older or simpler leaf shutters can be quite durable, and they may outlast older fabric focal-plane shutters. One reason is that focal-plane shutters move more mass over a larger distance, and older cloth curtains can be easier to damage. Leaf shutters are also often enclosed in the lens, which may reduce exposure to dust and handling damage.

But modern comparisons are less clear-cut. Leaf shutters used in some compact and mirrorless cameras may have lifespans roughly similar to mid-range DSLR focal-plane shutters. They can exceed some entry-level focal-plane shutter ratings, but they do not necessarily outlast high-end modern focal-plane shutters, which can be rated much higher.

So the claim is only partly true: leaf shutters can be longer-lived than some focal-plane shutters, especially older or lower-end ones, but not all. You really have to compare specific shutter implementations rather than shutter type alone.