I will say that I always had store update notifications showing when I would wake up at 6 am. This was like clockwork since I got the 920 in November. Starting this month, my notifications are now coming in at around 7 pm. I don't remember when I got them on my Titan II.
I know that I am not getting them later then before. When I would get my 6 am update, I would see the updates almost always before they were posted here on WPCentral. Now with them arriving around 7 pm, WPCentral has already reported them.
My routine has not changed either. The only thing that did change, but could just be a coincidence is that my battery did completly die early this month in the evening. I had to charge from a completly dead battery. After that, is when I started to notice my notifications coming in at 7 pm instead of 6 am.