WW is an awesome strain, but I wouldn't call it couch-lock: it's a very relaxing and cerebral stone for me--one of my favorites. So you can see on that chart what more amber would do to the plant... I'd harvest now, and I'll bet the high's gonna be dynamite, but in a really good way.
I'm growing some heavy-duty couch-lock/good for insomnia strains right now for total relaxation and de-stress. One is Mazar: "Good mental high; potent, physical, powerful yet relaxing. Couch lock" and the other is Afghan Kush: "Very Narcotic, insomnia, good for pain." So like Mazar would be good for watching a movie or chillin with friends in the evening, and the Kush will be good for, well, getting sedated.