I usually ask during the interviews to avoid unnecessary stress. POIs normally reply within days while programs usually take longer. I would avoid emailing them within the time frame they provided. If you didn't ask, I think two weeks after you talked to a POI or one month after the program interview would be a good time to follow up (just my opinion)? If the interview happened not long ago, you could always send a follow-up email to thank them for their time and casually ask about the timeline.
I am done with most of my interviews and waiting for them to get back to me (they told me it would take a few weeks), so I got myself a 2000 pc jigsaw puzzle to kill time lol