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Track mode basically dials down the stability control so you can go more sideways and put the power down more aggressively out of tight corners. The biggest effect would be increased tyre wear and a bit more stress on the drivetrain components, half-shafts in particular. I wouldn't worry about the brakes for road use. Only prolonged track use would give the brakes a proper workout.
I would imagine you can switch track mode on all the time, otherwise it would have to be geo-fenced to every track.
I tried the Track Mode for the first time today. To your question of driving on it all the time I would like to mention two observations: 1) the "Hold" function does not work so well even when the H sign is shown - the car can still roll slowly. 2) the regenerative brakes do not work so well either even when setting is on 100%. Both 1) and 2) are noticeably different to the car performance without the Track mode. So be aware of it.
Keep in mind that the cruise control does not work in track mode, and the fan noise is loud. So maybe increased wear and tear on the fans, conversely with less battery issues due to the better increased cooling?