I think most people don't realise that since the Ffestiniog Railway turned into an experience, there are generally only one or two departures a day to/from Blaenau.
Even in the height of summer, I can't see a day with more than three. (Someone prove me wrong!)
Clearly that has fairly obvious implications for Round Robins, if you are trying to factor in possible delays somewhere on your journey.
That is correct. However, pre-covid when there were more services to Blaenau, very few of them made good connections. And unfortunately some of those that did, often ran near empty in one direction or the other many days.
Nowadays, there is the Quarryman service, that starts and finishes at Blaenau, and is timed specifically to connect off the morning Conwy Valley train, and connect back onto the Conwy Valley service on its return to Blaenau. As this service is specifically designed to connect. it is probably the best option for those doing the round robin. There are also the services that start from Porthmadog, one or two a day depending on demand.
However, everything is likely to change next year when the Conwy Valley timetable changes. It doesn't look to be good news for those wanting to travel to and from Blaenau, as the proposed timings seem to be aimed more around the Bettws market. Which is understandable, as most times the Conwy Valley trains empty out there.