tapering before a marathon

Question
I am just a recreational runner, 46 years old, who has completed 3 marathons. I'm slow and steady with a PR of a lengthy 5:45. I jumped into training for the LA Marathon late this fall and 3 weeks out will get to 20 miles for my long run. My total weekday mileage has only been 10-12 miles with some cross training in between. Question - Should this 20 miler be my last long run at 3 weeks before? I plan on only doing an 8 miler the weekend before, however, what length should 2 weeks out be? There are so many opinions on the internet.

Answer
On most things I see for marathon training, the 20 mile mark is well-enough to get you prepared to finish a marathon.  However, with your daily mileage being 10-12, I imagine you could go longer if you wanted to.  I think 20 miles is at-best a conservative approach to keep you in top shape before a marathon.  Basically, you don't want to run a marathon's distance twice within 3 weeks, that's why its recommended to be a 20-miler on most programs.  I don't really know what length 2 weeks out should be though, as I'm not that familiar to marathon training with my clientele in the past.  I'm mostly a "5K & Under" guy, such as cross-country and track distances.  

Rick Karboviak