Yes, not knowing the timeline is the hardest part! A couple of tips based on my experience:
Medical Exam: When you get the instructions sheet for the interview (it will come in the email) you will see that your partner will need a medical exam at a specific doctor in Lima. It has to be 2 weeks before the interview. I recommend following up a week later to make sure the doctor sent the report in to the embassy. Ours had not arrived and caused a delay. When we called the doctor after the interview she just said "oh, lo siento joven, lo mandamos hoy"...... so easily a delay that could have been avoided if we had been a little more proactive about following up.
Police Reports: The instructions we got said to bring the police reports even if they had expired. When we got to the interview they asked for updated reports. I would take the expired ones with you but go ahead and get updated ones if you can to take as well. This will help avoid a delay.
Updated Forms: The same thing goes for any forms that might be "out of date" or from the year before. We were asked to get an updated affidavit of financial support only because it was signed last year. Of course, this is because of the delay on part of the embassy BUT it is something I could have easily had ready before the interview if I had known they would request it.
Upload: Any forms you update- police records, financial reports, etc- I would go ahead and upload them on the online platform. Maybe you could call the file "Updated forms date___." Many people had updated forms on hand but the agent still gave them a "rejected pending documents" because they needed them in electronic form. If that happens it isnt a problem, they didnt request that we go back for another interview but it just adds time to an already long process.
Good luck!