Like any computer, the lifespan of an all-in-one comes down to you. All computers will degrade over time, while new software evolves and grows more demanding. You should replace your PC when it isn’t able to handle tasks quickly. If you use your AiO for work, for many hours each day, you may start to see the slower performance that warrants an upgrade after 3-4 years. If you only use your computer occasionally and don’t care much about performance, it may seem fine for a decade.