How much sleep is enough?

Hello, we’ve got a wonderful 11 weeks old Shiba puppy. Lately, she’s been getting really overexcited, especially in the evenings—she jumps around, bites, and doesn’t listen. She also has a hard time falling asleep. The breeder, whom I actually consider very knowledgeable, says this is a sign that she’s not being challenged enough and that 18 hours of sleep a day—which is actually our goal—is way too much. She says she needs to sleep much less and be exercised much more so she doesn’t get overexcited in the evening. But I can’t quite believe that—everywhere on the internet says that puppies need a lot of sleep and that being overexcited in the evening is a sign of overtiredness. So what’s the right thing to do?