They'll never give gems as prizes. That's just making the coiners coin less.
Prizes are so that the coiners will coin more.
You can't exclude winners from competing again. These are the top coiners usually, and letting them not participate is bad business.
My suggestion is to split CWF into different brackets, mixing things up each month for variety.
That is a valid observation Herby! How about this then? Move all winners into a seperate warfare event! They fight it out for grander prizes/bragging rights...and thus frees up opportunities for other players to grab a slice of the pie, and progress as well?