yep, you would have a smaller yeild. supposedly...
now, hypotheses come into play. others have tried this, i have not, so i can't offer my oppinion on this method. but...
supposedly you can flower with 12 hours of dark followed by 6 hours of light. this is done with a digital seven day timer, and is supposed to take a couple of weeks off the flower time. a day is only 18 hours instead of 24. you trick the plant into finishing earlier.
i watched a log where someone did this a couple years ago. they ended up with great results, but yeild was lower than that of his previous grows of the same strain.