<p>I am attempting to find xml files with large swaths of commented out xml.  I would like to programmatically search for xml comments that stretch beyond a given number of lines.  Is there an easy way of doing this?</p>

Considering that XML doesn't use a line based format, you should probably check the number of characters. With a regular expression, you can create a pattern to match the comment prefix and match a minimum number of characters before it matches the first comment suffix.
http://www.regular-expressions.info/
Here is the pattern that worked in some preliminary tests:
```
```
<!-- (.[^-->]|[\r\n][^-->]){5}(.[^-->]|[\r\n][^-->])*? -->
```
```
It will match the starting comment prefix and everything including newline character (on a windows OS) and it's lazy so it will stop at the first comment suffix.
Sorry for the edits, you are correct here is an updated pattern. It's obviously not optimized, but in some tests it seems to resolve the error you pointed out.