To brick or not to brick??

Brick a week is good.

Yes, you should train.

My dog gets ticked off at me when I go out for a bike ride.  So most of the time I have to take him out to the nearest trailhead, and slowly run after him.  I always have quivers in my calves.  Hopefully the more Bricks I do, they will go away.

At least once a week.

Better to feel them now and know what is happening to the body than have it happen on race day.  Which I learned the hard way.

madcow is right. You don't want to do more than 10-20 min at easy pace. You just want to get a feel on how your legs perform after the bike. It also helps you to test how well you replenished fluids/energy while riding. Bricks longer than that take a big toll on the body; hence it takes longer to recover.

Go forth and do the brick.

I go out on Sundays to do my brick at race distances (to simulate race conditions) and also do short runs after a bike ride. This helps teach the legs to run fatigued.

My only advice is to brick, and then brick again!

I try to do a 1 mile run after each bike ride, this helps me get use to my pace and heart rate.  I will be increasing the distance as times goes on.  I don't know if its beneficial but it does make me feel more at ease for whats to come.