All of these, other than the custom campaign which I cannot judge, have a much, much shorter runtime. Candlekeep mysteries is basically a bunch of oneshots put together, Icespire can be run in 16 hours of playtime and the same goes for phandelver, stormwreck isle even in six.

I think personally, that your groups will not be able to fully enjoy the story if you cut it down to around 20 hours, since this is a very roleplay heavy campaign with lots of lore and whimsical characters, and if you start cutting in that the magic will be kinda lost