I'm not extending the deadline. Everything I do, its always "extend the deadline". I let this one go for 2 weeks - that's more then enough time. If people haven't come up with something in 2 weeks then they don't really care to do it if I make it 3.
If contests aren't important to the community then that's fine, I can do without the time it takes to come up with them and just make any decisions myself.