i think it depends on the learning style, but yeah, i was doing 60-80 a day during dedicated. at least on days i wasn't purely doing pathoma/FA. i do agree that there are diminishing returns with the more questions you do. for me, two blocks a day, with reading explanations carefully and rechecking the FA section for that question, was plenty
edit: i want to avoid identifying myself but like i said i scored about a 260. once you are above 255 differences in score don't really matter FWIW
i guess if what you're asking is "is it possible to score 260 working no more than 8-10 hours a day" then the answer is yes. if you already have a great knowledge base and study efficiently