Plumbers typically say that a toilet can last around 50 years. However, this is only true for toilets that are well maintained and gently used. If the toilet was improperly installed, it might not last as long.
Getting a replacement flush mechanism can be more difficult with dual-flush models. Each manufacturer can use a different mechanism, whereas there is a standard for standard flush mechanisms. Finding these parts is often quite tricky. Usually, you have to go to the original manufacturer to get the parts rather than the local hardware store.
Dual-flush toilets have mechanical valves with rubber seals in the cistern. These are used to allow water to flow when flushed. That rubber seal can deteriorate rapidly. They are also prone to be blocked by debris like porcelain or grit, causing the water to flow continuously.
Dual-Flush toilets have two buttons built into the cover of the water reserve. One is used to flush solid waste and the other to flush liquid waste. The biggest advantage of dual flush toilets is that they save around 67 percent of water used compared to regular toilets. The solid waste button uses 1.6 gallons to flush. The liquid waste uses 0.8 gallons or half the amount of water.