My routine for taking Humira is pretty simple. I take the Humira out of the refrigerator and put a timer on for roughly 20 minutes to let the Humira sit. Also I make sure I have an alcohol pad (Humira includes some in the Humira). Once the timer goes off I check the Humira to make sure it is clear. Then I rub the alcohol pad on my thigh and wait about 30 seconds. I then take the two caps off the Humira pen and then make sure I have a song I really enjoy playing right before I inject (honestly I have never had a leak when I play music while injecting Humira).
I don't know if there have been any studies done of people who don't rotate their injection but my guess is it wouldn't really change a whole lot. To me I would rather get 100% of medicine rather than injecting into a place were I may only get 80%.