Matthew Walther recommends 100 pages per day, rain or shine, weekday or weekend, holiday or holy day or ordinary day. Paul Griffiths, by contrast, recommends the following:
You need a life in which you can spend a minimum of three uninterrupted hours every day, excepting sabbaths and occasional vacations, on your intellectual work. Those hours need to be free from distractions: no telephone calls, no email, no texts, no visits. Just you. Just thinking and whatever serves as a direct aid to and support of thinking (reading, writing, experiment, etc.). Nothing else. You need this because intellectual work is, typically, cumulative and has momentum. It doesn’t leap from one eureka moment to the next, even though there may be such moments in your life if you’re fortunate. No, it builds slowly from one day to the next, one month to the next. Whatever it is you’re thinking about will demand of you that you think about it a lot and for a long time, and you won’t be able to do that if you’re distracted from moment to moment, or if you allow long gaps between one session of work and the next. Undistracted time is the space in which intellectual work is done: It’s the space for that work in the same way that the factory floor is the space for the assembly line.
A friend of mine finds this vision more attractive, because (a) it measures time, not pages read; (b) it implicitly incentivizes 25 dense pages of Aquinas over 125 pages of Mickey Spillane; (c) it’s devoted to intellectual work of whatever kind, not just reading; (d) it’s an achievable minimum within most kinds of adult working life; (e) it focuses on lack of distraction, rather than finding tiny slices of time in which to digest a few more pages; and (f) it allows for weekly and annual sabbaths, in which intellectual labor may rest.