should be totally fine in veg, might be an idea to knock it back in 1/2 hour steps over a week or two.

another note on a simmilar subject, i work a really wierd 12 hour shift pattern, somtimes days, somtimes nights, my plants are flowering.
but theres been occasion where i get home just as the lights are going out, not giving me enough time to perform some maintinence.

so what i did was kept the lights on an extra 1/2 hour, and knocked the timer back half hour, so instead of say 7pm-7am dark, it became 7:30pm-7:30pm.
not ideal, but no hermies yet!

if you really have to mess with the cycle for some reason, i think damage limitation is key, you want to be as little intrusive to the plants routine as you can.