I would be happy to end a cycle and reboot while the books are dominating the sales. Going out on top is a good thing! People will remember the great previous cycle, the new cycle will benefit from that and the readers are already there and will probably be interested in checking it out.
If you wait until sales are down the toilet all you get is whining how the cycle started out great but ended shitty and you have to try to win back customers.
Publocation cycles would be great, they would be even greater if Marvel and DC had the balls to ditch the monthly books and the direct market. They write for the trades anyway, so just release the stories as trades from day one!
Let the comic shops die, they ruin the image of superhero comics, in the eyes of many people they are dinky shags where nerds live. The aren't even enough regular comic book readers to justify catering to them, ditch them, rebuild your audience and if it doesn't work give up and stop publishing comics. At this point DC and Marvel probably make more money from Batman and Spider-Man pyjamas and lunchboxes than from the comics themselves. They should concentrate on makind animated and live action movies, tv shows and DVDs. The lowest rated episode of Smallville had 1.9 million viewers, that's still an audience 20 times bigger than one buying Superman comics. It's really sad how pathetic the comic book numbers are.