If someone throws a dinner party in your honour eg. You're newly married and they want to have you over with your in laws, or it's your birthday and they'd like to throw you a little party.. once that is over, would you phone the host to say thank you? or send a thank you card afterwards? Or would you say thank you on the night and not contact them again?
YANBU - it's enough drawing thanks on the night and getting in touch with the host after that night
YABU - you should phone after the event to reinforce your thanks or send a thank you card