I did a Topdeck tour last winter (did the Winter Spirit). It was absolutely exhausting but I had such a blast.
I’m not a huge party person and was spending all my money on two months away, so I didn’t want to waste it all on drinking.
There are so many people on these tours that you will always have a group that are happy to stay out all night drinking, but there are also heaps of people who are there mainly to see the sights of Europe and are happy to just have a drink or two and then call it a night.
My tour group and leader were also pretty fabulous and there was no pressure to stay out all night, or to do all the optionals etc. I doubt I will do another tour again but if I did I wouldn’t hesitate to tackle another Topdeck tour.
Hope this helps,