Newcomers can be awesome
There are lots of clever people in the world. People who never previously contributed to your project can be really bright, smart and write incredible code that pushes your team forward already in their first contributions. When responding to questions and providing review comments on changes, remember that being new in the project does not necessarily imply that someone is a rookie in any other sense.
Sometimes you get the best patches and help from people you never met before and who move on the next day never to come back. The open-source community can be a warm and fuzzy place!