We have always stated that all elements of the entry must be taken over the weekend of the competition and that was clearly stated at the top of this thread again - as usual. Of course anyone wishing to dupe others could do so as exif data woudl not give them away but it would be hoped that in a fun competition all would stick to the spirit of competition and meet the terms. As for timescales I am sure for a competition entry someone a bit useful with photoshop could come up with such as the pig image int he timesacles and am pretty certain oggalily did so last time as it was a rule then I believe. If people are going to take so long in editing an image that it takes longer then look for a different image!
Sorry - later edit after seeing other contributions. If someone is willing to work on 3 or more images and do the shots in the weekend why would we stop them. It is a personal decision. I did a composite of 3 images a couple of weeks back fro resolution and had intended doing 5. True it was pretty rubbish and I could only use 3 in the end but it took me little longer than a single image I did the following week. I was using the subject to teach myself morwe about photoshop as much as anything else. Pointless bannign composites - if people want to do them fine - it does not mean the will be necessarily better than an image that someone took on the spur of the moment and uploaded as an out of the camera jpeg
PS Anyone seekign further inspiration here is a longer list of possibilities alphabetically:
http://users.tinyonline.co.uk/gswithenbank/sayindex.htm