Knight on f8?

I've heard that keeping a knight on f8 (or f1) makes it really difficult to checkmate a king that has castled short, and in my experience it's worked really well. But is it worth keeping a knight inactive throughout most of the game?

Where did you hear that?  

You've probably also heard that "knights on the rim are dim." Guess what? A knight on f8 or f1 is on the rim. (Because it can only control 4 squares versus 8 squares when it is more centralized.)

There are undoubtedly some defensive positions where it is very helpful, but a knight on f8 (or f1) can't participate in most attacks and certainly is not something you want to do as a general rule.

http://www.chess.com/article/view/the-power-of-positional-chess-pt-3

I also read that f8 is a good defensive position for the knight, I think from a book, but I don't remember which book or where I read that.

In answer to the OP's question, I don't know, but I strongly suspect that that advice is only for during defense from a strong kingside attack. Obviously you don't want to leave your knight there in the endgame after the attack has dissipated (or succeeded!), since you'll need that knight to attack some pawns and to escort your pawns to promotion. Also, if your own attack elsewhere is succeeding, you'd want that knight to join in the attack, so again I believe that advice is only during a period of pressured defense. I believe the advice was to contrast with a knight being located at say e7 or g6, which are poor defensive positions for the knight.

I just heard this note and have decided to give it a test. While it doesn't insure "NO checkmate..." having a Knight on f1 or f8 seems both hard to achieve and does seem effective in at least blunting a strong Kingside attck.

"So much fun, with a Knight on f1!"

No good player has ever suggested just keeping a knight permanently on f8. But a knight on f8 is a very reliable defender if your kingside is being attacked. In that case, the knight is not inactive at all. It is efficiently performing an important defensive job!

Yep - I've had a Knight on f1 for 15 moves and it is doing yeoman's work!

Here is example, not sure if it's good move order, though. 

Knight on F8 stops the mate, knight on F1 stops the fun

I just ended a game with Nf8#

Knight to f8, never mate, the GMs say...

BUT WHEN A KNIGHT IS MOVED TO F8 WITH CHECKMATE...