Usually, the life of most water heaters, even the most efficient, is around ten years, give or take 8 or so. This is for tank water heaters, not the tankless variety. There are many reasons for this. Mainly, with tank heaters for water, there are many different parts and that is why they have more that can go wrong with them than tankless heaters. Tankless heaters flow water through a high heat valve and heat it instantly as it is flowing rather than store it all up in a tank. They are more expensive, but in the long run they do save more money on repairs. Find out more when you look up on demand water heater reviews.
This is why you want to convert to a tanklesshome and save yourself a whole lot of trouble: For example, with tank heaters, there is a pan at the bottom for collecting mineral deposits which form from long standing heated tap water. These deposits can eventually clog up the pipes and blow the whole system out. A word of warning is to notice the popping and crackling sounds associated with this symptom so you can call a professional plumber after finding some reviews and then hope the clean out fixes any problems. Tank heaters are simply unreliable.
Sometimes replacement is a better option than repair. If you have a tank water heater and it is constantly having repair issues, you are paying more than you need to pay and that is the whole problem. The best thing to do is replace with a tankless water heater and avoid accumulating added repair costs. Tanks also have to be insulated. This is another issue which can go wrong because if a release valve becomes blocked then heat builds up inside the tank and the insulation makes it worse. The idea of the insulation is to conserve energy, but when the product is in disrepair, the opposite occurs.