You got it, that's how it should be! You should be a programmer instead of support
Anyway here's an example of how your code could be messed up:
When global search is checked, as part of the search, you cycle over all opened log files, and look for where you can apply the highlighting.
This is obviously not necessary yet, because we're looking at a different file at the moment and don't care about highlights on other files.
I'm guessing this example is not so hypothetical, because I'm getting 4x speed improvements when I turn off global highlight - from 8 seconds to 2 seconds, and the problem only really appears after I've been running LogViewPlus for a while (again, up to 22MB across 19 log files now).
That said, searching is still too slow after that ~4x improvement, so I'm sure there are other issues too.