I can't answer that question. I've had PSUs that lasted until I ditched them and others that failed withing a few years. Normally a quality PSU should last at least 10 years, but some will fail early.
Again total wattage means nothing (it actually is a 450W unit); the 12v rails is what's important with modern systems. I know that I won't convince you, but for a few more euros (7 to be exact), you can get the much much better Antec Basiq VP-450P.the LC Power office is the cheapest one and has 600 watts the lowest