Not only do nitecore chargers cut off at 4.2 they also automatically lower charge rate when getting close to 4.2.
Ive seen it go from 500 to as low as 20 thats why the final stretch takes the longest.
I usually discharge to about 3.8 and it charges relatively quick, never timed it though.
Its pointless for me to use a 4bay charger i can usually charge 2 sets while sitting on 2 cells.
Remember even though its an advanced charging system you shouldnt use batts straight off the charges, give it some time to simmer.