S*o why does the challenge have to start at the begining of each month... You take 4 weeks say for the challenge entries, then a week for the voting. Then after that start another 4 weeks + 1 week voting.

*Overlooking winner announcement time and time for winner to pick a new challenge.

Then you are close to bi-monthly and it is easier to keep track of deadlines. I've said enough.  I've cast my vote.
ps

The mods time and devotion here have to be considered also.  

2 months is a good length for a challenge, hence the current system being voted in. It eases the mods workload somewhat, and it affords the artist time to explore different aspects to the challenge theme. With the current challenge, for example, I've had time to work on 4 scenes. You won't be seeing any of them because they're all terrible (I can't model in Bryce for toffee), but IF I'd liked them I'd have just chosen the one I preferred most and entered that. In short, I vote C. Besides, I like the status quo. @dhama - If you like entering challenges so much, why not enter the challenge arena and have a go there?