For as long as I've used WinRAR (~8 years) I've never had any kind of popup or anything to nag me, not sure why :shrug:. It may be because I just save all compressed files to my desktop and use the right-click context window to extract them.
Yup, you won't be nagged so long as you only use the context menu and DON'T use the options that open the archive window. It's only when WinRAR's archive window is displayed that it'll nag you.
That said, I'm more for 7-zip these days.