As for series, if I get invested in the world and characters, I sometimes read longer than I probably should. (Sort of like how I would sometimes watch a TV show past its shark jump, riding the memories of its glory days and hoping against hope they might return. Once in a blue moon, it would happen... usually not.)
That is well put.

I have a tendency to not finish series, for a variety of reasons.

1. The series becomes just too big and clunky (Wheel of Time, Dune)

2. I can't get past the awful writing and plot twists (Wither, Ringworld)

In the latter case, I rely on Wikipedia and Goodreads to tell me how everything ends up.