Re: Why is the duty cycle so low?
It might be necessary to have that dead-time to allow the IR receivers out there to 'reset' or something, so that the TV-B-Gone doesn't interfere with itself?
Just a guess, but I have noticed that the TV-B-Gone interferes with remotes, so after a tv has gone off, the regular remote is useless until the tv-b-gone has finished sending all its codes and goes to sleep. So even with the 1/4 second gap it's sending fast enough to block other remotes.
Still it wouldn't hurt to do some empirical testing, and see if a shorter delay still works.