Explain reason for length of GIF

In order for a GIF to loop smoothly, its duration is based on the longest effective period of rotation, growing (changing size), or glowing (changing colour). If one of these is very long (i.e. changing slowly) the GIF will be long. This is not clear to most users, and they may be frustrated when they try to create a GIF and it takes forever and produces a huge file. It would be nice to show something in the 'loading' screen while a GIF is encoding explaining which quiggle and which aspect is responsible for the duration and suggesting speeding it up if they want a shorter GIF.