I have been taking it for 18 months and have always taken it at night as I go to bed. Working on the principle that I will sleep through any side effects! So far so good and I sleep ok. Also hot flushes disappeared after a few weeks too.
I too take mine in the morning; I take mirtazapine at night and when I was prescribed both that was how I was told to take them. Without the mirtazapine I struggle to get to sleep too; Tamoxifen doefishermen to cause insomnia, even though I don't get hot flushes or night sweats! I've heard the side effects are worst around 5hrs after taking the pill, but that may be anecdotal rather than scientific fact.