Unfortunately DH only does flying one night trips and spends most of that in meetings but he has visited the Hermitage and said it was amazing. I'll go with him one day, just haven't had the chance yet!
I agree with your husband that the Hermitage is amazing. When I visited it in 1993, I saw a Bible that had so many jewels on it that I would not have been able to put my little finger down without touching two or more jewels. I also wound up in one of the basements which held a pre-historic exibit. Thought I was going to get locked in for the night.
I love St. Petersburg. So much history, so many beautiful buildings and the food was wonderful. I would love to go back again. The boat cruise on the waterways is a wonderful way to travel. The other time I visited, we took the train from Moscow to St. Petersburg.