How often or when do you know to change brake pads?

[BikerBoy]

Searched around and didnt find any answers. Ive heard they tend to last forever on the gs500. So should you replace it due to age or use? (ie oil or brake fluid is changed 2 yrs or 3000 miles as an example)

[Kookas]

Look down the disk at the pads and see how much material is left. Your pads might also have come with wear indicators (grooves in the pads), you should replace these if you can't see the indicators.

[Toner]

Searched around and didnt find any answers. Ive heard they tend to last forever on the gs500. So should you replace it due to age or use? (ie oil or brake fluid is changed 2 yrs or 3000 miles as an example)

I think if they hit 2mm if you don't have a groove indicator.

[Watcher]

There is no interval of time/mileage, pad life depends very highly on the rider.

You can look at the pad and see how much "meat" is left on them, from there just use your best judgement.  If they look thin, change them.  If they look fine, leave them alone.
It's not rocket science, really.

If you're on the fence about whether or not you should, it may be an ok idea to pair that service with a bigger job.  For example, brakes are looking and you're near the wear-bars on your rear tire.  The wheel has to come off the bike for a new tire anyway, may as well just do the brakes while it's easy to get to.  Pads really aren't expensive, anyway.

[Kookas]

That said, I remember thinking I had hardly any brake material left on the front - I didn't have much braking power and when I looked down the caliper it looked like one pad was quite thin and the other was crushed against the disk. Ordered in some new pads and pulled the caliper off only to find those pads actually did have plenty of life left, before I got my greasy, brake fluid covered hands all over them thinking they were toast. I could probably have sanded them down or something, but I already had the new pads. Those old pads now sit at the bottom of a milk bottle I use for bleeding to provide ballast.