output to background nested screen stops until foregrounded

my typical setup is a nested screen--one screen session running on a box, call it box1, holding five windows, each running an ssh to a different box, call them box1 through box5, each of which runs screen again. most of the inner screens will have at least one window running a process that continuously produces output (something running inside `watch', a `tail -f', etc.).

if i leave that window as the current window on that screen, then switch away from that on the outer screen, and leave things that way for a long time (e.g. overnight, about eight hours), then when i go back to that screen, i find it hasn't updated in hours (the clock in the caption line shows a time well into the past). when i begin to issue any screen command (just hitting C-a a to send the command char to the inner screen is sufficient) it starts outputting all the updates in rapid succession. if there are a lot of them (e.g. if it was running `watch' on its default setting of "update every two seconds"), this can take several minutes to finish.

how can i change this? i'd like to have inner screens continue to redraw themselves whether or not they're currently visible in the outer screen.
-- 
Aaron Davies
[email protected]