How do you know when to replace pads?
How often/ when do you usually replace your pads?
I just check my pads and they are worn a decent amount but still have some meat on them. I've had them for almost two years. I'm wondering if I should go ahead and get new pads now or wait another season.
Check with the manufacturer of the brakes, i.e. the instructions that should have come with the brakes. If you don't have them, visit the manufacturers website and hunt around in the Tech section. There is usually no "time frame" for replacing pads, it's usually done based on the thickness of the pad. For example, Avid pads should be replaced when the pads, including the backing plate, less than 3mm thick. This requires removal and measurement. Most manufacturers use a similar method of gauging pad wear.
Also, a suggestion. Since your pads are two years old, I'd recommend having a new set on hand. It sounds like your current pads still have a little life left in them. Whether or not they'll get you through this season is debatable though. So rather than wait, have the pads on hand. It'll save time.
"I do whatever my Rice Cripsies tell me to!"
Check to make sure the springy thing that pushes them apart is not about to rub on the rotor.
Look at the entire circumference of the pad contact area, if any point along it is worn too thin, it's time for the pads in that caliper to go. It's too thin when any part of the pad other than the braking surface (plate, spring, etc.) is about to rub against rotor. They also make a distinct noise when worn past that point.
They may also need to be replaced before a long ride if there's a chance the pads might wear out before the end of the ride. Rain and mud can wear pads many times faster than in dry weather. You'll need to start the ride with good pads if you expect them to last through rough conditions till the end of the ride.