Longest I ever did was 1 hour (on film in the late 70s) ..... it was nice , but that was very nice and worth seeing , nice time lapse too ....
I'm actually doing a set of 3Omin 35mm widefield SCP star trails to pick the best location for my permanent pier (near the garage and near the old slab in my backyard) .... will help in sorting SCP alignment too ,.,,, just a little.