As a passenger, I have always felt like the engine are not kept at take-off thrust/full throttle a few (tens of) seconds after take-off, and so for obvious reasons as fuel efficiency, engine wear prevention, noise control for population in airport area, and so on.
I have also read on this site or on excellent Twitter account of the A380 captain Dave Wallsworth lots of explanation about how to reduce the take-off thrust (eg. flex temp).
But I cannot find any information about the throttle level (N1 percentage may be more accurate) during cruise. My guess is it is not constant because of weight decreasing during flight due to fuel comsumption, but this is only a guess.
I know Airbus airliners have a "CLIMB" position on throttle which allow the autopilot to set N1 automatically to reach cruise speed, but I would like to know how N1 value evolves during cruise.
A320 throttle quadrant with lever at CLIMB position, with auto-throttle range: