Honestly not sure. It's short, like 15 minutes max iirc. I either don't have the permissions to see where this is configured or don't know where to look for it. Maybe someone who can will see this thread or I can try find out if you really want to know the number.
I can't do this test, but if you want to know how long, make a new post (or try with the one you just did) and attempt to edit it every few minutes. I am not sure if this timer is based off the original post time or the last update time so it might take a while
That or make a new post each time and progressively wait a longer period each time.
p.s. Did you get my email a while back?