Drip systems last for around 10-20 years. You'll know it's time to replace your system when you start to see multiple underground leaks. If you've had 3 leaks in recent months, the line under the ground is getting brittle so it's likely time for replacement.
Timeclocks are not all the same. The cheaper ones just don't last very long. We only use Hunter outdoor timers that we've found are easy to use and more durable controllers for your sprinkler & drip systems.
Valves are usually in a tan or green box in the ground. They open and close to let water into the pipes that run around your yard. Cheap valves don't last very long so we only use light-commercial quality valves. Valves go bad in various ways - they lose pressure, they leak, they won't shut off, or sometimes they just don't turn on at all.
PVBs (pressure vacuum breakers) are the weird looking things next to your front yard faucet. They kind of look like a mushroom. They stop yucky outdoor water backing up into your kitchen and they can turn off the water to your yard when there's a problem like a bad valve. In Arizona, every home is required to have a PVB to be considered up to code.
We offer a 5 YEAR warranty on new drip or sprinkler installations (all but the heads), timeclocks, valves, and PVBs.