I can't do more than one for-others reading in a day - and not more than three in a week (unless I did absolutely nothing else that week, presumably, but I haven't had the leisure to try that!). If I could do more, I'd be doing it for money by now.
I have twice done that for a month, and was burnt out.
I also haven't found a way of making a reading last less than an hour, of which half an hour is actually reading (with the cards, and making notes) and then 3- to 60 minutes typing it up (during which I get a lot more insights so the reading isn't complete in the "untyped" first half-hour).
I don't think it's "intuition exhaustion" exactly; my intuition and/or spiritual sense and/or picking up on things unseen and unspoken... whatever it is... gets a lot of exercise most of the time. Reading the cards is different somehow and I wish I could determine what the difference is. The empath part of me gets a real workout in a reading! Which may be it now I come to think of it - I live comfortably with that part of me "in hand" from day to day but if I rein it in when reading, my accuracy dies. Aha. Thanks for this question, it's given me a clue to this puzzle! Maybe, then, it's "empathy exhaustion"?
Not sure I'd want to read with the empathy switched off, if I even could; it wouldn't feel honest.
Reading for myself rarely takes more than 10-20 minutes, with a lot more cards than I use when reading for others. I find it necessary to use spread positions for myself, as I can't trust myself to interpret by "feel" when I'm personally involved, though I don't generally use positions for others. In fact for others my standard reading is two cards and that takes the time I describe and produces 300 to 1200 words of write-up.