Longest session I ever paid for was 3.5 hours.
Longest session I ever had, put paid least was 6 hours. I had been playing softball in the afternoon and I pulled a muscle (hamstring) in the back of my leg stretching out a run to first base. The pain was of the "holy fuck'" variety.
After about an hour I managed to drive to my favorite spa. I limped in the door and my favorite MPA, Cindy, immediately became concerned. She helped me undress, shower, and immediately placed me a hottub for 30 minutes. She then had me lay down on a table where she gave my legs a rubdown. She had me drink a bottle of water, then back in the hottub for 15 minutes, then into the steam room for 15 minutes, then on the table for another massage session.
At this point the owner and his wife (I had met them on a number of previous ocassions) came in to see how I was doing. I assured him that I would pay for all of my time. He waved it off - he insisted that as a regular customer it was the least that they could do for me.
I stayed until the end of the night - Cindy kept moving me from hydro-massage, to steam, to massage table. At midnight she started our last massage, a long slow sensuous session that end with us both on the table cuddling. I walked out the door, with my leg only a little sore.
Although I attempted to pay Cindy, she would only accept our usual fee for an hour's NR ($160). The owner, who saw me to my car would accept nothing, saying that it had been his pleasure that they were able to help out a regular customer.
Needless to say that after that experience, I stayed with that particular spa for years. Now I know that some of you are wondering where such a wonderful place is - Edmonton in the mid 80's. The name of the place was Spa & Suntan. It was a combination of a regular health spa (with execise and weightlifting equipment, treadmills, bikes etc) at one end, tanning salon in the middle and MP at the far end.