I don't bother to check physically on pad itself.

When you car is new or you just change brake pad, the brake fluid is at Max position. Once the level goes down to Min, you know that the brake pad is about to be replaced. The pad probably good for many km perhaps. I just change since it is not that expensive for my MyVi

When you change brake pad, the brake fluid is still in the brake closed system. When replacing the pads, brake piston is pushed back and the brake fluid level will go up again to F or H. If it is slightly less, then just top up a bit to serve as new monitoring indicator

The brake fluid change I think is not by mileage but time based. Some recommend once a year and some every two years. You can flushed it any time you want and it is not labor intensive procedure which may be completed in half an hour perhaps.

Me? My MyVi follows service schedule of 40k KM for brake fluid change but I've not change the brake pad yet as far as I remember since it is not under scheduled service I think. On my older car after scheduled service, I did not change brake fluid even more than 2 years. Yes, people said not good, said carbon deposit whatever. Sometime I just cahgned when I remembered that I did not changed it for so long Don't follow me