Sure it does.

If you have demand for 10,000 passengers to be transported on a route daily, and a plane carries 200 people, you would need 50 trips. If the round trip is 4 hours, you could do 6 trips per plane and you'd need 9 planes to service the route.

If the round trip time is 8 hours, you could only do 3 trips per day and you'd need 17 planes.

It might. Going faster likely increases wear on moving parts, which would presumably result in longer ground times for more frequent maintenance?