When you move from five minutes to ten, do you build out or join two bits together?

I’m trying to make the jump without ending up with ten minutes that feels like two separate fives stapled together. Is it better to take the strongest five and deliberately deepen a couple of bits, or start joining material that already works and worry about the shape later? I can see how adding more detail gives you a more coherent set, but also how it could turn a tight five into a baggy ten.