<p>a) There is no hard retirement age; that was outlawed in the US in the 1980s or so because it’s considered age discrimination. Professors can remain teaching as long as they like, with many teachers teaching well into their 70s. However, the majority of them earned their PhDs in their 20s and 30s and began teaching in their mid-to-late 30s.</p>
<p>b) Probably not. There may be individual professors or even programs that have a prejudice against older students, thinking that they are less likely to successfully enter academia or research fields. But there are many programs that do not have that prejudice, so you can get into a PhD program somewhere, I’m sure. There are also some fields where that may be easier than others - in one of my fields (psychology, not clinical) it’s more uncommon for someone past their 30s to start a PhD program, but in my other (public health) most of the students are older and have pursued some kind of career first.</p>
<p>I will say, though, that you may encounter some difficulty finding tenure-track academic jobs if that is your goal. Some people will be unable to reconcile their image of a new assistant professor as a bright-eyed 30ish-year-old with you, and some will have flat out prejudice against your age. Others will be worried about your longevity in the department - they expect a 30ish-year-old professor to remain in the department for 30-40 years, but with you nearing 60 by the time you finish your PhD, they may see you as only “good” for 10-15 years.</p>
<p>c) No. Nowadays even lecturer positions are competitive and being filled by people with PhDs. This is especially true if you desire to enter the humanities.</p>
<p>Also, were I you I would disabuse myself of the notion that I could “fast track” a PhD in 3 years. PhDs in the US typically take at the very least 4 years, as you will likely be required to take at least a year of coursework even with a prior master’s degree. More commonly, they take 5-7 years, and if you are in a humanities field, I would up that estimate to 6-8 years.</p>