It's a good point. For me it depends at which stage of the course the student is and how comfortable is with the flying.
If done SL already, introduce cruise checks, if cruise checks already introduced request a lower speed straight and level and then a faster speed SL.
If you can allow turns, slight turns to certain headings (30 left, 45 right, 15 left) . If advanced and posible, PFL. Or ask her him, what if the engine fails now?.