Example:

I'm struggling a little bit in game, and getting bored.  I decide to exit the game to do something else, and I get the message:

"Are you sure you want to quit?  A few more turns wouldn't hurt..."

OK, OK... I'll keep playing a little longer.

Eventually, I start having fun.  I'm even pretty excited.  I've got plans and things in motion. I'm offered a Draginol Quest - sounds even more fun!  So I take the quest, complete it.  I am now eager to get back to continuing my other plans when I hit the turn button and...

Game Over, You Won!

Hold on, Wait a minute!

When the game is boring, it asks me to keep playing.

But...

When the game is fun, it tells me I have to stop.

Think about that for a second.

Proposal:

Let the player decide when the game is really over.

When a Victory Condition is met, show the player the Victory Screen, but give them the option to continue playing (having fun).

Otherwise, players will have to waste time avoiding things that would otherwise be fun.