Break pads - how do find if they need replacement

[Kisu_san]

Hello,

I have a dumb question. Today I took my car to local garage for winter tyre change and mechanic told me I need break pad/rotors replacement.

And also said there is a rubber boot back of the disk, close to shock absorber is also worn out.

I don't have any warning signs on the dashboard. I bought the car when it was 100k kms and now it is close to 130k KMs. I don't know when the previous owner changed break pad/disks.

My breaks working ok. I did not notice any noise. a year ago another local garage guy make rotors(disks) sharpen on lathe machine, I dont know if that is good thing to do.

BMW E53 X5 3.0i 2002.12 Euro model. Miles - 130K kms

1. Is it always you get the break pad worn out warnings
2. Does anyone know if this model car equipped with these sensors?
3. Would it be needed to change the break pads before warning lights goes off.

thanks in advance