One thing a lot of people do for NeoLemmix packs - and if I'm not mistaken there's no reason this can't be done for SuperLemmini packs - is, if there's a lot of music, they put up two seperate downloads; one for the music and one for the other content. This way, if you need to update your pack, people only have to redownload the relatively small content, not the large music files.
(To be clear: There's no forum rule or anything saying you have to do this; it's just an idea that works well for a lot of people.)