What if after you've cleared all the arenas and claimed the prizes, as an added bonus, you could return to the arena of any element, without winning the prizes of the chosen arena of course...lol. Meaning if you want to return the water arena, you can. If you want to go to the pure arena, you could go there too. The best part of this is that you can also use this to train and level up dragons. Food for thought.

@don-pablo-escobaro why would any one go back in arenas if we are getting better rewards

@amogh-sai agree we can get better reward , don't forget more arena u enter more difficult to win ... if ur dragon lv 20- 30 .. can u beat enemy dragon's lv 40-70 ... not including empower too .

I don't understand why you would go back to the lower arenas once you complete them all. We already have the master arenas, and they change every 3 weeks or so. So we continue to have opportunities to upgrade various elements in the arenas.
Besides, a veteran player going up against the novice players fighting the lower arenas for the first time, really isn't fair.