I may get shot for saying this but it has a lot to do with who I'm with ..... I always do hours and if the young lady is not charging a premium and I have had a good time I will tip.  For the more expensive ladies I must admit I don't really know what to do  ..... not many of us make $300 or more an hour ..... but I also understand they have travel expenses and aren't working (at least I hope they aren't) 8 $300 sessions in a day ..... good question ..... I have tipped in both situations and not tipped as well ...... I welcome the input

appreciated but NOT expected. As an independent, although my consideration may be listed on here on my TER profile, I do observe the "competitive" going rate in cities I tour. If that means I have to offer a slight discount to have interest I do. When friends "tip" me, it is always so appreciated but certainly not expected. It shows me that my new friend or even my regulars appreciate my service and understand that traveling has it's own expenses. I don't treat my friends that don't "tip" any different though, I still do appreciate that you reached out to get to know me and I can add you into my friendship circle.
Lastly, "tipping" doesn't have to come in paper form, it can be simple: sometimes I ask if you can bring a bottle of water, or a bottle of wine for us to share, a snack,  etc.