I just bought this game (I'm at least a year late for most games) and despite only putting a couple hours in I've been getting As and Bs on the Score Attacks and Time Trials. I'm surprised by how well I'm doing; I'd figured the scoreboards would've been dominated long ago by people who could put many hours into honing their scores, and dilettantes like me would have no chance.

So are the scoreboards periodically refreshed to keep newbies in contention? Are they not all-time scores?