We are adding a new feature for special situations where you want to light your model with a long, narrow light - Linear Lights
A Linear Light can be sub-divided into multiple light sources - which causes the illumination from the light to be more even, and causes the light to converge faster (fewer passes) when rendering.
Linear Light (bottom) and Rectangular Light (top) after 20 rendering
passes.
BY the way - if you do this by hand, by placing multiple, small, rectangular lights - which will work just a well as the new linear light - be sure to cut the wattage of the sub-lights.
If you replace a long rectangular light of 100 watts with 8 shorter lights make them 12.5 watts each (100/8)