Per Toyota, 10 years is the time limit for the original coolant in the engine. In this video I use 50/50 diluted concentrate + distilled water coolant that is good for another 5 years.
I am NOT doing a flush as that would leave an unknown amount of city water in the system, along with chemicals such as chlorine and fluoride. If I can't get all the flush water out, it would dilute the incoming 50/50 mix and would not give the engine full antifreeze protection.
There is no block drain on the back of the engine (cost reduction).
I'm also changing the hoses. Probably not needed, but I don't want to take the risk with 10 year old hoses. The smaller hoses will likely be OK as they are stressed less.
Edit - This guy had a hose failure at 250K & 15-20 years • How to swap out a Toyo... - edit
The hoses have spring loaded clamps that can be set in the open position. I show how to do that on the car and on the workbench.
Discovered a new to me filling tool, that is cheap ($20 on amazon) and works quite well. Wonder how long those have been around??