It honestly varies. There is no normal.
Like I said, could be an hour, could be all day.
You can always Google "ESO server status" if you feel you need to watch out for it.
I suggest doing something else for a few hours...play another game, read a book.
ZOS why cant you offset the 20 hr daily items, like randoms as well as riding etc by the amount of time it takes for an update, or BETTER YET, get rid of the 20 hour crap and just have them all as part of the normal day like writs etc