when do you change out bicycle disc brake pads.
 

i'll ask it here so i dont get foolish responses i would get from MTBR..about upgrades.

how do i even know? i've been downhilling unlike a boss lately. a lot. i'm on those levers often and long. my local park has some terrifying downhill sections. rocks the size of baby heads all over.

At least once a year. If I'm on the brakes a lot as you are describing much, much sooner. It takes longer to get a bike in a stand than it does to pull the pads and look at them to see how much pad is left. They are pretty cheap and I always have a spare pair at the bench. Worst case you can pull them, clean everything up and put them back in.

+1^ they are so cheap and so easy to change and at the same time so critical to riding that it makes no sense to try to defer changing them.

On all my bikes you can see the remaining pad thickness while the pads are still in. When they get down to say 2mm on either side (because they don't always wear evenly) just change them.

Remember also that you can get different friction materials for different Seasons (e.g sintered / non-sintered for wet / dry)

You guys check your rotor thickness too or just wait for them to warp before replacing? I ask on behalf of my son who rides DJ, so his speed is usually checked by 10' ramps! No front brakes on that one, but he does have a downhill/MTB. Both are hydraulic.