90 days is a big marker for me. I haven't been able to do it (30 days for that matter) since I started down the wrong path four years ago. I'm counting up to 90 and after that, I'm just going to look forward to living sober and use my sobriety date to remind me of the day I finally started crawling out of the hole.
Whatever gives people the path of least resistance to sobriety is the one they should take.