So that code looks great, I decided it'd work however it doesn't, quite. Where the old form produces:

```
>= 0: 0
>= 60: 1
>= 300: 0
>= 900: 0
>= 3600: 540
```

The new form produces:

```
>= 3600: 2
>= 60: 2
```

I'm now creating a skeleton hash to pass in as the initial accumulator (that has all the ages as keys), and using `<< check` rather than `= check` :-)

works now