When you finally get ten minutes, how much of your reliable five do you keep?

I’ve spent ages treating “getting to ten” as if it means finding five extra minutes. Now I’m wondering whether that’s the wrong way to think about it. If your existing five is reliable, do you keep most of it as the spine and build around it, or use the longer spot as permission to replace some of the safe stuff with material that needs more room? I don’t want ten minutes to become five proven minutes plus five minutes of homework.