Menubar turns into drop-down too early

Hi, When I resize my browser window, making the width smaller, the header menu (with my pages) turns into a drop-down menu far too early for my taste. Is there a CSS way to control when this transformation “kicks in”? I would like to keep the individual pages buttons (there’s four of them) for as long as possible, until the smallness of the window doesn’t allow anymore. My site: lordinvestor.net Thanks!