Why is the onus always on the bottom workers to be honest? Why are we trying to feel guilty about our working hours vs how much we're paid? Because it's clear salary is not tied to better performers given how much upper management is compensated.
Just enjoy your life. Management probably lowballed you coming into the job anyway, but if they are happy with your work, then spend that extra time you're saving to enjoying other things in life.
What do you want to do, OP? The new year is coming up.