Boyznus:
Cool avitar.

Bh06:
I don't have a big room and an AC, but I don't see why you would need different temp settings. Why not just have the AC come on if the room gets too hot? I don't know, maybe 88F. Mine do just fine going up to 95 at times. Or is there something I'm not understanding?

I'm pretty sure purple kush will give you purple buds no matter what temp they are at night or any other time. I don't know what bringing the temp down the last few weeks will do other then slow down their metabolism. I suppose it would simulate the outdoors, but why slow them down if you don't have to. I've never heard of doing this intentionally, but I've only been growing a few years.