herky - when i see the orange middle and the small flame tongues, i also add them sometimes, but this seems more efficient. i don't think there is much problem with adding tehm at the stage you mention, but i do think it will take your unit a little longer to get where you want it to be. no big deal as long as a person is aware of it.
by waiting a bit and allowing them to get so they look like the picture above, i've noticed that because of the good airflow of the chimney they can get to a working temperature faster, which in turn helps your unit get up to a working temperature faster and more efficiently because you use less fuel to get to the same place. if you put them in before you are ready, the decrease i air flow (for me at least) leads to more "fiddling around" trying to get to the right temp or a longer wait. the wating isn't so bad, but i tend to get up later than i intend to and am constantly running about an hour alte on my smokes. this makes dinner time alte and mrs. taz is not happy. not good. as for the fiddling around, this can lead to overshooting your mark and your temp curves will look more like saw teeth.
these are my observations and experiences that seem to work well in my latitude (climate) that comprises morthern montana. as i always say, experiences vary and if anyone has a method that works well for them, they might want to consider this but ultimately should go with what works best for their needs.