CeCe, a couple things. First, when I eliminated benzos to practice TSM I started taking Trazedone for sleep. I'm 6'1'', 205lbs and 100mg puts me out though I have taken as much as 200mg on a given night. If you're so inclined run it by your PCP.
As for taking Naltrexone so many hours before actually drinking. This is definitely an issue in my opinion and runs counter to the standard advice we offer on the Options Saves Lives board. But for a few exceptions you want to take Naltrexone at the onset of a craving, then wait the hour so that your brain connects the craving with the unrewarded drink. That is a true extinction episode in my opinion. Additionally, by doing what you're doing it really doesn't provide the opportunity to say, "Do I actually want this drink". Instead, you're setting your routine up rather than actually deciding if a drink is what you want or need. Lizard Brain stuff which we're trying to avoid.
As for the people who disappear the school of thought I've understood is, 'why keep going to the hospital if you're not sick'? Or, perhaps alcohol has become such a non-issue in their lives why continue carrying on about it. This practice is definitely not like AA where folks are perpetually in recovery. It's a finite conclusion that one is 'recovered'. Of course there are those who this simply doesn't work for for any number of reasons non-compliance being the primary one.
I'm sorry you're feeling alone with your friend having a more successful conclusion or perhaps more apropos an earlier conclusion. Yours is still right around the corner.

You might be well advised to read through this link on 'mindfulness' for a bit of a refresher:
http://optionssavelives.freeforums.net/thread/645/mindful-drinking?page=1&scrollTo=6921