I haven't convinced myself to spend the money on zwift, trainer road is expensive enough as it is, and a lot more useful. OTOH, I think that I probably could tolerate longer rides on zwift. I have a lot of trouble doing 20 minute intervals on TR. I don't know if I believe that anything longer that 2 hours is really useful. One of the projects on my short list is a rocker plate for my trainer to make it a little less debilitating to ride for a long time. Trainer road will let you go month by month. Not sure if zwift will let you do that, anyone know?