the reason we want associated types/consts is that most benefits of Duration would come from letting the trait specify the timebase, so the driver can do all their maths in that timebase. For example, with fugit:

```rust
trait Delay {
   const NOM: u32;
   const DENOM: u32;
   fn delay(dur: Duration<u32, Self::NOM, Self::DENOM>);
}