A slightly different thought process to augment the other very useful answers:

This job can take up as much time as you let it. If working 60 hours at your salary satisfies you, go nuts. But the salaries aren't high enough to retire early, so you're probably going to be doing this a long time.

Otherwise, you want to protect your time not only by being efficient, but also by prioritizing those work tasks which are most important to your continued employment/promotion. As a TT prof at an R1, that's likely research. Papers, grants, etc. Teaching quality, when you come up for promotion, is often a pass/fail scale where "fail" is "consistently abysmal with no apparent improvement".

An option, then, is to be strategic in your course design to find a reasonable optimum trading off quality and time commitment. For example:

• Can you grade fewer assignments? Grade them using a method that's less time consuming? Give less student-by-student feedback and centralize by producing answer keys?
• Make slides that are decent without bells and whistles? Or if it's possible, teach more of your lectures as board or tablet written talks?
• Be more mercenary about your office hours? Write shorter emails?
• Follow a book more closely the first time you teach a course than you'd otherwise like?
• Optimize when you do longer grading more for when it is convenient in your schedule, even if that means delaying somewhat when students get assignments back?

My key advice here is mental: All other things being equal, you could almost always put more time into teaching materials, assignments, etc. and your courses would, as a product, improve. But one hits marginal returns. You might be able to produce an "85/100" quality course that teaches students what they need to know with much less time commitment than 95/100. I think for many of us, especially recently out of school, it's hard to let a work product be 80-85%. If your boss is asking for 60 hours a week of work and only paying for 40, though, something has to give.