Well, I figured it was a reasonable thing to do since there is apparently no limit (that I have found) on either the number of pictures, or the total aggregate size of all pictures, that can be included on an individual post. I've seen single posts from other members with over 20 pictures in them. At 40KB a pop, that can add up.
I do ensure that the composite picture will render correctly on a screen that is 1024 pixels wide. Very few people nowadays use a horizontal screen size smaller than 1024 (especially with the 16:10 aspect wide screens). I also try to keep the total size of the composite picture as small as possible. Most of the individual "piclets" are well under the FF size limit.
With plant id pictures in particular, one good picture is worth a dozen mediocre pictures.