popular myth.  not supported by fact or good shop practice.  ram the
pedal to the floor or you won't be bleeding all the contaminated fluid
out.  the argument about damaging seals is bogus - if there's anything
that's going to damage seals, you need to know about it /NOW/, not when
you're emergency braking.  and the argument about "it started leaking a
week after i bled the brakes - i must have pushed the pedal too far" is
also bogus.  you're introducing fresh fluid into the system.  fresh
fluid can shrink seals slightly.  if they're already worn, there's your
leak.

again, bleed the system with full pedal stroke.  if this reveals a
problem, be grateful to be on top of the situation.