Are you still going through UWorld on your first run-through? 40 days is a pretty good amount of time. I always did 46 random questions from all subjects, all unused until I ran out and started doing my incorrects on random. Even though I may not have necessarily touched upon or extensively reviewed the relevant content for some questions that would turn up in some of my blocks, I felt that it was still a decent way to go about things since some of the harder questions that I had little to no clue about would stick with me and help me tackle similar questions down the road.
I usually did 1 or 2 blocks a day early on and escalated to 3 or 4 later in the game. I tended to spend 2 to 3 hours reviewing a block (i.e reading the explanations, reasons why other answers were not applicable, annotating into First Aid and simultaneously reading the pertinent content, etc.), so I found that it was hard to do more than two blocks per day at first, but later sped up my review process (i.e reading the summary explanation at the end for less in-depth questions or the no-brainers). I feel like doing 3 or 4 consecutive blocks is more of a stamina-building exercise once you've done a pass or two of First Aid, so if you feel that you need more time to cover content to make the most out of your UWorld-ing, work that into your schedule as needed since you're the one who'll know best about what you need at a given stage in your prep.