Ultimately lots of people have lots of different opinions, so you might have to do what feels right for you! Since this school seems quite receptive to updates, I sent one 2 weeks ago just giving and update on my volunteering and some new tasks ive taken on at my current job. Nothing crazy substantial but just enough to say “hey im interested enough this school that im taking the time to write a letter becuase I do still want to go here!” But for other schools that seem to only want substantial changes, im holding off (until i have something substantial, like submitting a paper or starting a new jobs etc). Hope my (unprofessional) perspective helps a little. I also received both update emails. Target / good gpa but my mcat is on the lower end for Rush