I don't think we should hold back from concatenating if the factory recognizes that the files are from the same source. Why would a user NOT want the data all together in one DataFrame. For example

```python
my_lc = LightCurve([goesFile1, goesFile2])
```

I would expect to get back one GOESLightCurve, not a list of two. The only reason I would create a light curve in a single call like that would be to see them together. Also, if it was built into the factory then concatenation when multiple files need to be downloaded (which every type of light curve needs) could be used by all classes of LightCurves.