On the topic of GIF file sizes, maxlabor fleshes out* what was said about GIFs' lack of a "reference" frame rate:
[frame rate for gifs is] a result of how varied the source material is. i run into this issue whenever i composite more than one gif in {AfterEffects] and it's also interesting to see what happens when you do a similar operation on photoblaster.** people who work in data visualization often make gifs that are 100-200 fps, and have 7-30 frames. those who work in film and video (even animators) have to abide by motion picture / broadcast standards like 29.97/23.98/25 fps. people who make gifs from scratch can choose whatever frame rate they want in their various softwares and often choose more antiquated frame rates like 8 or 15fps.
and
if i take footage shot at 24fps and want to make a gif out of it, the frame rate dictates the fidelity of the gif. in the 360-frame gif you're talking about,*** there is no fidelity to speak of, because it is merely an abstract thing that moves nicely. fidelity doesn't really matter for most people on the internet, but i never remove frames from footage to reduce file size -- if anything, i edit the action (i.e. in and out points)
To each one's own - editing the length or number of frames is all fair game - it's the result that matters. Maybe you want the GIF to look like a poorly restored silent movie.
*he wasn't fleshing out so much as disputing the post before reading all of it (which he later thoughtfully acknowledged)
**a gif mashup site
***the giant one-bit GIF in question