Reverse SSH tunneling

[m g <tsilims gmail com>]

I'm trying to set up reverse ssh tunneling between two boxes, one
behind a firewall (the box I want to SSH to) and one that isn't (which
is ssh'able).

I've found ssh -R, but i'm wondering if there's a better way to do
this than leaving my user constantly logged in to both servers ...
specifically, I'm thinking that this is a security risk.  Any ideas?
-- 
MG