I've definitely seen TGV sell out in France, and would recommend buying your ticket in advance, depending on the trip. SNCF is sadly taking the airline fare rou

I've definitely seen TGV sell out in France, and would recommend buying your ticket in advance, depending on the trip. SNCF is sadly taking the airline fare route, with intricate pricing and non-sensical fare (sometimes 1st class is cheaper than 2nd class, and I'm not sure two people riding the same train pay the same price...). I hate this system with passion. But unless it changed recently, it's not quite like that with the shinkansen in Japan. I would usually buy a ticket in advance for a late time trip around 10pm (with reserved seat), just in case all shinkansen are sold out (never happened, but I'm the anxious kind). On the date of travel when I'm ready to leave I just go to the train station, and ask at the counter to change my ticket for the next shinkansen. It's completely free, including the reserved seat, although maybe that's only for the Nozomi shinkansen? Not sure for Kodama/Hikari. Never had an issue with the next shinkansen being full, but maybe I've just been lucky. I was mostly traveling between Osaka and Tokyo, where there is one shinkansen every 6 minutes at rush hour, and at worst one every 20 minutes. So in practice the waiting time was practically nil, and I loved the flexibility of being able to decide until the last minute to either dine out in Tokyo with my friends, or simply head back home earlier.