No time commitment in terms of how many rounds you want to play. You should be around if a question has been asked though. Like if you need to leave you should wait till a round is over between questions. Is that ok?
I ask a Q and you have 5 min to guess. 3 strikes or more than 5 min the other person gets to steal. If they steal, they get the points you had added up - if not you keep them.
If you just wanna try 2 questions (one for each) and see how it goes that's cool. You can say "last round or 2 more rounds" or something if you have to go soon. Fair nuff?