I'm at a SLAC that really values an open-door policy, flexibility in meeting with students, and a lot of attention to undergraduates at all levels. This policy is quite successful in many ways and I agree with many of the values that sustain it.
It is important to learn how to set appropriate boundaries in such a system. If you don't, you'll get eaten alive by thousands of little tiny mouths each taking a bite from your wriggling flesh. Yes, you need to prioritize your service commitments, make time for research, keep up your growing excellence in pedagogy, etc. Today, though, I want to talk about students.
Student A: I know you have office hours on Monday, Tuesday, Thursday, and Friday, but I can only meet Wednesday at 9 am. Can you meet Wednesday at 9 am? I'm really busy with my lab classes but I really want to understand implicit differentiation because I'm very committed to my education.
Professor: (internal sigh as a glance at the calendar reveals weekly squash game. Puts aside squash game because of dedication to accessibility and love of education.) Sure, I can meet at 9 on Wednesday. I'm glad to hear you're interested in understanding implicit differentiation.
Student A: Great! See you Wednesday and I'm really grateful.
Wednesday am: no student. 9:10 no student. 9:20 no student. 11 am no student. Email appears over lunch. "Dear Professor thanks but I figured out how to implicitly differentiate so I didn't come this morning see you in class!"
Repeat with Student B, Stokes' Theorem, with research time rather than squash. You can always do that research later -- this student needs you now!
Repeat with Student C, vertical line test, with faculty coffee hour. Coffee? Who needs coffee?
Repeat with Student D, exponential functions, putting off grading. Well, I don't mind that one (until students start clamoring for the graded work).
Repeat... no, I refuse to repeat.
This year my policy has been that I will not reschedule research time, Skype calls, my trip to the gym, or (most days) my lunch in order to meet with students outside of office hours. I will only meet when I'm genuinely free. I feel less resentful when they don't show up and more present when they do. I go to the gym and faculty coffee hour (or whatever) more often. What's most interesting is that students really don't notice or mind -- they are looking for the most convenient option for themselves but they are not surprised if you have another commitment at a particular time.
Today: "Can't come to office hours have class can I come at 1?" Email sent around midnight. It was the beginning of office hours as I read the email and started responding... and who walked into office hours just minutes later?
Don't think about it too much.