One is in engineering and the other is mathematics. In my program, we have a lot of master students who are working adults.

I say PhDs in the physical sciences are easier to get.

Programs that accommodate part-time students are, in my opinion, just doing it for the money. Part-time students are not awarded assistantships or fellowships; they pay their own way. It usually takes them well over a decade to finish, which makes their coursework outdated by the time they finish their dissertations and are looking for employment. In short, allowing part-time graduate students is just plain ineffective and inefficient in terms of producing competitive, employable, top-notch scholars.

And as I am sure you know, tenure-track professors work 50-70 hours a week as it is, mostly on our own research. Given daytime teaching loads, office hours, administrative burdens and committee work, asking one of us to teach or keep office hours on nights and weekends would be tantamount to asking us to abandon our own research, thus preventing us from keeping current in our fields of study, and thus precluding the possibility of promotion and tenure.

Tenured professors, who often teach less, but who spend equally huge amounts of time researching and writing, doing committee work, reviewing manuscripts, performing service to the discipline and profession, etc., deserve nights and weekends free to spend with their families, read novels, or otherwise relax — they’ve earned it, having spent well over a decade teaching, researching and publishing like madmen.

For this reason, and for many others, the graduate program I direct does not accept part-time students.

What are you to do? Well, besides telling your friend to finish his dissertation or he will be unemployable in academia (there’s just no good excuse for any full-time PhD student to take that long to finish), you must also decide whether you want to commit fully to working toward a PhD full-time — or not. Only you can make that choice.