Marathon Training Long Run Question

Depends on your fitness and what is your definition of "easy/light".

Well, not resting is not allowing the body to heal any microtears in the muscles.  Just my double pennies.

I am in the latter stages of training for my first marathon, and so what I say is most likely up for debate, given that...here's my take...

I'd say the most important thing is giving your leg muscles time to recover AFTER the long run.
I've found that it takes about 1.5 days for my legs to recover after a 20miler. After the short recovery, then I can run something between 7-12 miles without problems.  I suppose as my legs get more used to the long distances, my recovery time will be shorter.

For each "stage" that builds your long runs, the recovery time is needed after the "push" into new territory.  Rest, compression socks, food and adequate hydration.. Hal Higdon's plans suggest cross training ...such as light cycling, swimming the day after the long runs. I instead have been doing pure rest for the 20 milers. Maybe more advanced marathoners would have less rest, I would assume.

As to subsequent runs, I would agree that a light run prior to the "longest" run day is important. You should do a run on the prior day, that allows you to be fully recovered by the next day, when attempting your push run, IMHO.

The main thing is to listen to your body. Push yourself, but not over the edge. Part of the whole training strategy is of course to _not_ get injured, stay healthy and be able to reap the benefits of your training (duh). Easier said than done though...

Depends on the person.  How much running he/she has done, how hard he/she is running all the other training, current fitness level, etc.

I know many people who run 7 days a week, multiple times for most of those days.  It can be done, relatively easily.