Say I complete the learning cards in a deck for the first time in a day, but then there are more learning cards in the same deck later that day- whether the same ones or slightly different. Do I need to finish those that day or can I come back to them the next day? I am in medical school and with the firehose of information, I feel the need to still also progress to studying my new topics for the day. So, if I do learning cards once for a day, would you say that is sufficient to make steady progress for learning that topic?
The best practice is to complete all of your due reviews each day.
If you’re unable to do that, they will still be there waiting for you when you next sit down to Anki. 
Judging what is ‘sufficient’ for someone is always tough, as it depends on a lot of factors. The proof, as always, will be in the pudding
Happy to answer any other questions you might have about using Anki alongside medical school studies.
Thank you! You mean reviews as distinct from learning cards, right? Should the goal be to make all learning cards become reviews in the same day as first studying them? Do you know what it takes for a learning card to become a review card?
Reviews are distinct from learning cards, yeah.
For a learning card to be a review card you’ll need to successfully clear the learning steps you have defined in your settings.
For example, if your learning steps are set to 10m 25m 1d (just a random example), you would see the card once and, if you got it right, see it again in 25 minutes. After that 25 minute interval you’d see it again and, assuming you got it right again, you’d see it the next day. At that point, once the final learning step (1d) is successfully cleared, the card is no longer a new card.
This is a simplified example and there are other factors that come into play but as an example it works.
Only you can answer this question. Ask yourself: Do you have trouble remembering the learning cards you delay? Are you ok with these cards re-appearing day after day until you do review (or delete or suspend) them? Does it make sense to you to violate your own learning steps, or would you be better off just choosing different learning steps so that you aren’t reviewing sets of learning cards multiple times per day?