In my personal experience, game -prep- is just as easy at any level.
In-game rounds for combats seem to remain about the same average duration. (i.e. how many rounds it takes from start to finish is about the same, presuming that we stay in the same range of difficulty for encounters and don't spike up to be level+4 when all the comparisons have been level+1 up to that point)
Combat real-time duration does increase around levels 8-11, again a small increase around level 15/16. This is mainly because both PCs and enemies are flinging around conditions - some of which are easy to track/remember, others need that constant "I forgot what does that thing you do mean?" Of course, the more familiar the -players- are with each others powers and effects, the less that happens.
But back to the DM perspective, as said at the start of this little missive, regardless of level, I have found prep time to be constant. If I'm ever taking longer its for plot development story arcs (creativity on my own part), not for the crunch of encounters...
Again, all that just based on my own experiences -- your experiences can vary...
In-game rounds for combats seem to remain about the same average duration. (i.e. how many rounds it takes from start to finish is about the same, presuming that we stay in the same range of difficulty for encounters and don't spike up to be level+4 when all the comparisons have been level+1 up to that point)
Combat real-time duration does increase around levels 8-11, again a small increase around level 15/16. This is mainly because both PCs and enemies are flinging around conditions - some of which are easy to track/remember, others need that constant "I forgot what does that thing you do mean?" Of course, the more familiar the -players- are with each others powers and effects, the less that happens.
But back to the DM perspective, as said at the start of this little missive, regardless of level, I have found prep time to be constant. If I'm ever taking longer its for plot development story arcs (creativity on my own part), not for the crunch of encounters...
Again, all that just based on my own experiences -- your experiences can vary...