That makes sense.  I think I prefer moving ttl to where you have tags.  I also am leaning towards having one parameter for those, so if you just need a ttl, you pass it, but if you want tags and a ttl, or just tags, you pass an object:

```
cache.set(key, value, '5 minutes', done);
cache.set(key, value, { tags: tags }, done);
```

Perhaps we could do this later, but it would be nice to consolidate those params.