From here, I'd say that if you want to be comfortable riding long rides, you have to ride long rides. Riding a couple hours once or twice every month or so will not result in much of a training effect. But maybe more importantly--If you want to buy another bike to see if you like it, GET YOURSELF ANOTHER BIKE
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I don't do: disks, tubeless, e-shifting, or bead head nymphs. But I do hate all e-bikes.