I know somebody who did experiment with this a little bit, and I paid attention because free knowledge is never a bad thing.

He took 2 groups (G1 and G2) of identical clones. They rooted them in a bubbler, 24 hour lights on with some weeny CFL's, then when they rooted (all of the strong ones within a couple days of each other), he transplanted them to FF soil.

G1 received 18/6 for 3 weeks, then switched to 12/12 on week 4
G2 received, 18/6 for week1, 16/8 for week 2, 14/10 week 3, then 12/12 on week 4.

There was no obvious difference in each group. G2's slightly changing cycle did not trigger earlier vigorous bloom growth.

He is running 2 1000w lights, contained, about a meter from the plant tops, SOG.

Now, I think to get a more accurate understanding of whether a slowly changing light cycle or a sudden change is better to trigger vigorous growth, you'd have to stretch the veg cycle out much longer, maybe even upwards of 2 months!

But, what is cool about his experiment, is that we both learned that you can save a bit of electricity by slowly cutting back on light usage with no obvious negative side-effects (if you're doing a 1 month veg or less, can't speak for anything longer than that).

So if nothing else, you get an extra ten bucks to go to the movies or something each month.