I don't know if vroom can or will give you the ability to freeze newest nodes, but I'm working on a newest nodes client that behaves the way you want by default. It reads and analyzes a cached file of newest nodes data that doesn't change until the 'refresh' button is selected. You'll also be able to 'undo refresh' to restore the previous list.

I'll be carefully parsing this and other threads for ideas and suggestions (such as tye's thoughts on flagging replies to old nodes). Feel free to /msg me with requests.

ps - Here's an HTML screenshot of it's current state of development.