There are 4 major reasons, the biggest one is that with one release, I am extremely limited in what I can post. So lets say I have several thousand images of swords but I only have 400 that I have gone through and found the best ones and removed their background leaving me with 100. This means that I either wait until I have them all done and release one big pack that I can't later add onto easily without repacking, renaming, reuploading the whole thing or release smaller packs. Releasing one pack and updating it means a lot more work on my part and not being able to easily show that I've included changes to the pack.

Another huge, and I mean huge reason is releasing smaller packs means that I can having something to show for and share if I only feel like working an hour or two on images that day. It also means that if I'm bored of looking at swords and would like to work on something else, it doesn't hurt me because I'm not trying to finish one huge pack.

Also, as Midjourney improves, I have the chance to adjust the stats for a set of images, so lets say the current max width and height is 1024x1024, but it changes to 2048 x 2048, future volumes can just clearly state this change and I won't have a mix of sizes for a single asset. 

By being able to have a new volume of some set of images, I increase the amount of people that see all my available images on my page by having a new post show up in Most Recent Graphical Assets on itch.

Thanks for the interest and I'm glad some of the horses worked out for you. Hope you have a wonderful day LordEndre!