From MW 2022:
View attachment 646368
The multiple 2:30 pacers were split between s2 and s3. A good assumption we would see the same, but not a guarantee.
@Herding_Cats explained it well. To emphasize a key point, the earlier you start within your starting group the more time on course you will have. The sweep point maintains a 16 min/mile from the last person starting. Assume that person starts at 6:00am (not a guarantee, but a good assumption). At a 16 min/mile and a 6:00am start, they will finish at 7:39 AM (16 min/mile*6.22 miles = 1:39:31 hrs + 6:00am = 7:39:31 AM finish).
Let's assume you start at 5:52 am. You also need to minimally finish by 7:39am. That would be 1:47 hrs which aggregated over 6.22 miles is an average pace of a 17:12 min/mile.
Let's assume you start at 5:58am. You also need to minimally finish by 7:39am. That would be 1:41 hrs which aggregated over 6.22 miles is an average pace of a 16:14 min/mile.
Let's assume you start at 5:32 am. You also need to minimally finish by 7:39am. That would be 2:07 hrs which aggregated over 6.22 miles is an average pace of a 20:25 min/mile.
The sooner you start, the more time on course you get.
So, if you start at the very back and normally run a 14-15 min/mile pace for a 10k effort, never stop for pictures or anything else, then you will finish at 7:30am (14.5 min/mile*6.22 miles = 1:30:11 hrs + 6:00am = 7:30:11 AM finish). That means AT MOST you would have a buffer of 9 minutes to stop in character lines or whatever else because you have to finish by 7:39am. That 7:39 AM time is an assumption and not a guarantee. Things happen and the races can be delayed or rushed to start and change the normal timing. So don't hold me to the 7:39am projection. In the moment, the people on bikes are your best indicator as to how close you are from being pulled from the course.
Bottom line. If you run a 14:30 and start near the very back of the race, you will be able to stop for 1-2 characters in total during the entirety of the race. The sooner you can start, the more time you'll have for extra stuff.