Most of the anime I watch that I find myself enjoying, I will watch them through to the end, particularly if they're under 100 episodes. The longest ones I've watched all the way through that go beyond 100 are Fairy Tail and Dragon Ball, both the original and Z. Haven't seen all of the other series though, if we're counting sequels. Interested in watching Daima all the way through though!
With Pokemon, I've seen it all up to about halfway through of Diamond and Pearl. After that, only bits and pieces.