Cycles: tweak progressive refine tooltip to make it more clear

intern/cycles/blender/addon/properties.py

@@ -286,7 +286,7 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
                 )
         cls.use_progressive_refine = BoolProperty(
                 name="Progressive Refine",
-                description="Instead of rendering each tile until it is finished, refine the whole image progressively so rendering can be stopped manually when the noise is low enough",
+                description="Instead of rendering each tile until it is finished, refine the whole image progressively. This renders somewhat slower, but time can be saved by manually stopping the render when the noise is low enough.",
                 default=False,
                 )