I have written several Python tools for my company.  Is there any good reason to convert them from Python to C# now that their usefulness has been proven?  Would I be better off just leaving them in Python?
Some reasons that come to mind:

Performance 
Easier to find developers
Huge huge huge developer and tools
ecosystem

But I second what the others have stated: if it ain't broke, don't fix it. Unless your boss is saying, "hey, we're moving all our crap to .NET", or you're presented with some other business reason for migrating, just stick with what you've got.
Is there any good reason to convert an app written in python to c#?