The whites should stay on as much as you need them to. 7 or 8 hours of viewing time is usually sufficient. Don't think there is more PAR and/or intensity in the whites, as they (white or blue) put out about the same PAR.
As for placement, I'd probably lower them a bit if they are shining in your eyes while viewing the tank, otherwise you don't have a lot of sps
, so don't really need much more intensity than you have....but in that case i would lower them a bit. Are they turned all the way up?