If your water heater is over 8 years old we are most likely going to advise for you to replace it. The reasoning behind that is most warranties for water heaters end at 6 years and water heaters in our area last 12 years. So by the time you pay for parts and labor of fixing a water heater you could be getting close to buying a new one and with water heaters not always being the easiest thing to diagnose exactly what is going wrong, you could end up having more repairs in the future.
However, we will inspect the unit to make sure it not a simple fix in which case we will absolutely fix it. If it is under warranty, we will get the necessary parts from the manufacture, but you will still be responsible for labor.