How long should the videographer be present?

I would probably hire the videographer for the same amount of time as the photographer. I'm not sure if that's typical or not, but that's what I would do personally.

Ask what they normally do. You never know what they might catch and you'd likely miss some things if they leave early.

You should clarify with him/her on what their normal duration is.

They might also have packages of different hour times

I would do how ever long the photographer is staying , the videographer should too

My videographer came early to get drone footage. She was there 9 hours total. I don't have the full edited film but here is my sneak peek:
https://vimeo.com/447008005?ref=em-share

Daughter's photographer was with us almost 12 hours -- 11 am for getting ready thru the very end of the reception at 10:30. Her videographers were there for 7 hours -- 1 pm (first look) thru the bouquet toss and cake cutting and were done at 8 pm. Her package included all the raw footage (about 6 hours worth) and a 7 minute highlight film.

It depends on what you're doing and what you want to include. If you're having getting ready photos with your photographer, do you want the videographer's to film that too, or could they start when you're already dressed or when you're just zipping/buttoning/tying up your dress? For the reception, if you're doing the traditional things, you'll want to make sure they capture your first dance, speeches, bouquet toss, cake cutting, etc. After your main activities are done, they can probably leave because you most likely won't want to watch people drunk/tired people dancing badly in an emptying space over and over, but if you're having a send off, you'd probably want them there for that. Basically, you should figure out when the first and last things you want filmed will happen and that will give you your timeline.

Our videographer will be there the same hours that the photographer will be there.