You can of course make any rules you like, but restricting it to such a short recent time may be prohibitive for some people. Like if you have a demanding job. If you're physically disabled. Such pressure of time may help some people  achieve better results, but for me taking photographs is for fun and relaxation. If there is a 'hurry up already' element in this activity too - I wont participate.
If I thought about the specific subject of the competition, and produced something worthwhile showing off, why does it matter when I did it?
As a compromise, could you make the limit something like a year? many art competitions require that work be 'recent'  but define it as 1-5 years...

Sorry if I sound rude, I didnt mean to, but its frustrating.

"I paint that which comes from the imagination or from dreams, or from an unconscious drive. I photograph the things that I do not wish to paint, the things which already have an existence."
Man Ray, modernist painter
http://artpearl.redbubble.com/