My only advice to the company that conducts a contest like this is that they must give chance to others, I mean old winners must be restricted of entering after some time. With the skill they already have, it will now be easy for them to win.
You can see the same winners for almost every contest, and Roobet allows that because again this is an art contest that are open to everyone who wants to participate, this may look unfair but again Roobet is just being fair to everyone here. If you think they are good enough for that contest then try harder, we cant always win here. Just try to participate every contest, and youll feel the excitement and the disappointment at the same time. Restricting them might not be the option.
I always check the entries for each art contests and almost always I can agree with the winners. It is difficult to decide, as everybody has his own taste what he really likes or likes to see in an art piece, but in the end it is the Roobet team to decide which they deem the best!