I have seen Dodge pickups, Jeeps, Hondas, etc. with over 500,000 miles. I have also seen one or two 4Runners on this forum showing almost 500,000 on the odometer. It's certainly possible to go a half million or more in modern vehicles. The key is maintenance. It takes a lot of money to keep going that far. Everything for these Toyotas is expensive.
At some point, I think you get to the point where it's not economical to keep sinking money into a vehicle and it's better to replace it. But you've got a long way to go.