The longest drama i've seen has 150 episodes, the Pink lipstick.
It depends on where i watch dramas, if it really caught my interest and it has too many episodes, i always buy DVD copy of it then watch it time to time.
But if its less than 50 episodes, i watch it online.
The number of episodes doesn't matter to me, as long as it is tolerable, enjoyable and still giving me benefits, i will definitely finish it.