I have put many series on ice maybe half-way thru, for few months, but eventually returned to them to finish. Sometimes the dramas can become very hard to complete, so I start watching a easier series.
I have dropped the following
Introverted Boss (wasn't engaging enough for me)
Queen for Seven Days (way too drawn out and plot not engaging)
Revolutionary Love (just disliked the ML actor, way too overhyped personality)
Strongest Deliveryman (delivery to nowhere for me, some fun moments though)
Sungkyunkwan Scandal (great FL, but I didn't know where this story was heading... just actors having fun acting as clowns in a historical drama... and everybody dressed identically made tracking who is who difficult)
The Secret Life of My Secretary (can't remember, dropped after 1st episode)
The Uncanny Counter (too weird concept, lost interest)
But I might restart them again or finish from where I left.