Use your judgement. My point is that if you have...
...on one page:
```
{% compress css %}
<link href="nv.d3.css"><link href="foo.css">
{% endcompress %}
```
...and on some other different page...:
```
{% compress css %}
<link href="nv.d3.css"><link href="Different.css">
{% endcompress %}
```
Then, their combined names will be different and thus the user will download the content of nv.d3.css twice and no browser cache in the world will help him.
I think this is more important than to reduce the number different files. The optimization trick of clumping lots of files into one is more necessary when your visitors just visit one page and not likely come back to click multiple pages.