How much time does teaching and research take? Here is an answer (by Richard Felder in his must-read piece The myth of the superhuman professor):
It is no secret that research is a major time sink. It takes time – preferably in large uninterrupted blocks – to define problems, generate support, collect, read, and understand all relevant published work on the topic, plan a method of attack, make false starts and wander down blind alleys, wait out the inevitable unproductive periods, clean out logical flaws or weak points, replicate experiments, explore possible consequences and applications of results, write papers, and give seminars. Doing all that is under any circumstances a full-time job; doing it well enough to gain national recognition – now the principal criterion for promotion and tenure almost everywhere – requires an intensity of effort that tolerates few distractions.
That excellent teaching takes just as much time and intensity of effort is not as well appreciated. Consider the preparation of lectures. Most course notes and texts are written from the point of view of someone who already understands the concepts; the trick is to find a way to make the ideas clear to someone approaching them for the first time. Just stating a concept is likely to be useless. To make it comprehensible to most students, the instructor must first provide examples to establish relevance and motivate interest, then imbed the concept in a web of alternative expressions and visual representations, and finally provide more examples and participatory exercises to solidify understanding. Finding a way to do all that for just one relatively straightforward concept can take hours or even days – and a course contains lots of concepts.
Making up good problems is another time-intensive chore. Students almost never learn anything nontrivial in formal lectures; they only start to get it when they try to solve problems. For true learning to take place, however, the problems must vary in scope and difficulty – some drilling basic concepts, others integrating new and prior material, and still others challenging the problem-solving skills and creativity of the best students. Relatively few textbooks offer problems that provide the necessary variety and scope; the burden on the instructor is to collect problems from several sources and to make up and work out solutions to others. Doing so takes immense amounts of time.
The entire piece is very interesting, relevant and very readable. Take a look!
PS: Hat tip to my colleague Rajesh for the pointer to the piece!