I don’t recall the number, it's probably buried in an old trip report somewhere, but we had 2 hours solid riding on Swarm once. This was a photoshoot for the park organised through Thorpe Park Mania to photograph the ride with riders on for press release when backwards Swarm was that years thing. I'd guess about 30 circuits?
It was freezing cold and soaking wet, still great fun though. I know I felt rough the next day, just like a big hangover.
14 in a row in the evening on Zadra, which was disorienting to say the least, did 8 re rides on shambhala with express pass this year also. Most in this country was 10 in a row on Nemesis on a weekday.
I once had over 50 rides on Harry Potter and the Forbidden Journey without getting off. I also stayed on Test Track for so long that I was the only person left on the ride. But that was during a 'technical rehearsal' when it wasn't open to the public.