Is it critical to change coolant at 100K?

[komichal]

Just a few notes from me:
- before you start draining out the coolant, set the cabin temperature knob to max
- by draining the coolant via the radiator petcock you will not get out everything. I can drain slightly over a half of the coolant only. There is a petcock on the engine that allows you to extract some additional liquid but it is a rusty one - IMHO not worth it (it is like 2-3 dcl only), especially when there is no chance to lift the car up
- I am draining and refilling the coolant once a year. I know it is waaaay too often, however it is a 20 minutes easy job and this way the "old" coolant that stays inside the car has no chance to get "too old".
- I agree that original Toyota coolant is naturally the choice number 1. However, I do not use it. I use Sheron Antifreeze G12 which can be bought already 50/50 mixed and the bottle costs around 7 USD (4 times less than original Toyota stuff). This Sheron product won in the test of several other brands available locally and it matches the specs required by Toyota.