Arrival at Wimbledom 62 minutes after touching in for a tram will trigger an incomplete rail journey. As no end to end tram journey takes more than an hour, I believe that this is effectively a maximum journey time for trams. I’m not aware that it’s publicised anywhere, but if you’re still on a tram after that much time then it would be difficult to claim that you were acting legally unless there had been serious disruption.
As for buses, I didn’t think there was a maximum journey time. When the RPI boards the bus they log in to the bus reader and download the cards that have touched in during that journey. Only those cards will pass the inspection. This may explain why the driver didn’t say anything. It does appear that there may be a maximum to cover the eventuality that the bus doesn’t properly clear it’s database at the end of the journey. I’ll have to make some enquiries about this. Certainly 2.5 hours would seem to be enough for an end to end journey in all but the most extreme cases.