If you install a new version of LW, you'll lose whatever's installed at the moment!!

That update nag is really misleading for Pro users - says "Free" update but what it doesn't say is that the free update is for a basic (free) version . If your Pro benefits are out of date then you can't download any more free Pro unless you pay again.

If you don't have your Pro installer saved, or if you're not eligible for any more free Pro updates then don't update. You'll end up losing your Pro;)