Being on top

Had the day off Friday and made a visit to my daytime CF. Mind you, this is in Minneapolis where mileage runs low and extras are very rare, but my crazy Russian dancer and I have a long history and are very comfortable together. During our chat time before heading to VIP she mentioned her birthday was a couple weeks prior. I joked that I should have come in that day to give her some free dances. Fast forward to our time in VIP...two-thirds of the way thru our time together I reach completion. We cuddle for a bit and then she asks me to get on top of her and deliver those birthday dances. She was on her back horizontally on the couch so we basically were in missionary position. She turned out to be a very demanding customer and told me just when and where to focus my attention. What surprised me most was that I instinctively stopped when the first song ended...she laughed and pleaded for me to keep going. It was a hot time and I was amazed how quickly I adapted to the role reversal. The bouncer was a little confused by what he saw when he came to say that time was up. Fortunately, my horny dancer wasn't ready to stop so we kept at it another 3-4 minutes after he left. My only question, how much should she have tipped me?