I usually do it based on what I'm cooking. I'm feeling lazy I'll bang the meat veggies out under the broiler, or if it's a burger just do it in cast iron.
Really though, after using the Weber charcoal starter cubes last night it's changed my whole grilling/time allotment perspective. It is literally just as fast as waiting on the oven to hit 450 and isn't any harder than pressing the buttons to select the oven temp. For $3.99 for 24 cubes, it's almost free if you ask me and you ain't gotta fool with paper towel/newspaper/cooking oil and you get a solid light right off the bat, no fighting it. It ha literally made me think I may never use my Weber Gasser again, it's that easy.
The temp outside does a lot to whether I want to do it or not as well. Smoking is a different story, but grilling is affected a whole lot depending on if it's cold around my house. I'm really cold natured.
Clean-up is about 10 times faster too though and a lot less pans to deal with.
Weber Spirit E-310, Weber Performer, Weber Smokey Joe, Mini-WSM, ECB Electric.