If you've truly been following that "take it before 8 am" rule for 15 years then it seems like you are doing a good job of at least coming down so as to be able to sleep. It shows good self control, too. The coke I'm not so sure. ( 9pm quickly becomes 10pm, becomes ??? with that coke-driven urge to redose) Personally, I think every drug on the planet for me should be taken early in the day so as not to fuck with my sleep. Another thing I'd say, in my very humble inadequate opinion, is that, though benzos work nicely to take the edge off for sleep, they still don't make for good quality sleep. Any drug fucks with your natural sleep patterns, including alcohol. So keep the benzo dose as low as possible. Besides, when you wake up all groggy from benzos the next day, it's awful easy to want to get an energy bump to "feel like a normal human being again" and there is your lousy slippery slope.
But by asking the question, I'm wondering if you are sliding on that slippery slope a bit? You doing ok?