I myself only have GIMP to hand edit images, so I know the pain of doing possibly hundreds of them at a time. A completely arbitrary rule that I go by, especially for less popular girls, is I try to get at least one image in ten different actions besides Profile and Presented to consider it a proper pack. It seems like a weird number, sure, but it's worked for me a lot.
So, the thing about all of this is... doing what you feel comfortable with. If you can bring yourself to put out a pack with hundreds of images, then do so. If you cannot, then do what you feel is enough. I've always tried to optimize my packs to have smaller images and be a smaller download, but if I was committed to that fully, I wouldn't have done a pack like Yuyuko, which is 404 images, or one of my mostly .GIF packs which can reach well over 100MB in size.
Besides all that, I always fully expect people to start modifying my packs on their end. Getting rid of images they don't like, pruning out larger ones if they feel like it, adding in new ones, changing file names, etc. because at the end of the day, my personal preferences are still reflected in the packs, even though I try hard to remain neutral. I've downloaded plenty of packs and altered them myself to my own liking.