I can't recall if I saw Whitesnake once or twice. I will have to bust out my handy dandy concert list and check.
Wish I had such a list. I have no idea how many times I have seen some bands. Whitesnake is easy though. 3 times:
-Saw them sandwiched in between Kick Axe and Quiet Riot on the Slide It In tour (which means I got to see them with Sykes). I didn't know them at the time. I was there to see Quiet Riot. But they put on a great show, and I went and bought the album because of that. It became one of my favorite albums of that time period.
-Saw them on the S/T tour, as mentioned above. This was one of my favorite albums EVER, and they were the main reason I went to that show. It was Adrian and Vivian on guitar at this time. The extended guitar duel during the solo on Still of the Night was epic.
-Saw them headline on Columbia, MD on the Slip of the Tongue tour. Great show. Vai got a solo spot in the middle of the set where he played some songs off of Passion and Warfare with the band. He did The Audience Is Listening and For The Love Of God. There may have been a third song as well--don't remember. I think it also did Coverdale well to have a break in the middle of the set, especially given how challenging the stuff on Slip is and the fact that they were doing a longer, headlining set. I think Faster Pussycat opened that show, but may be misremembering. Tried to confirm by looking at their tour page, but it didn't say who was opening on that leg. But interestingly, it also doesn't list a show for Columbia, MD, which is where I saw them, so...