With large scenes, such as those rendered in real space dimensions, it's important that the fall-off distance is appropriately set.
Select the spotlight, and then look at the Object Properties palette. Select Total Falloff Distance in the pop-up. The value set in the numeric field to the right of Total Falloff Distance controls the extent that the Point Light will cast any light.
The default setting for Total Falloff is 1000 inches or model units. It's important to check this setting, and make sure it's proportional to the size of your model and the distance you want the light to go. Also check the Full Intensity distance in the spotlight's Object Properties, this controls the extent of full-intensity light cast by the spotlight.
These same principles apply to point lights.