Very hard to recommend a idea mileage a chain and cassettes will last, so many factors involved, use of cycle, type of cycle, weight of the rider and his or her riding style and under or over maintenance. Most generic chain and cassette makers are the same people that provide the named products. In the many years (55 ish) I have been cycling I have never broken a chain (that's a dangerous statement to make) personally from my experience I junk the chain at 3000 miles, with the Cassette I replace it when the teeth are showing some wear, sometimes at the same time as the as the chain. You can over clean your chain, If you are cleaning it every few rides you must make sure that when you relube the chain, the Lube gets into the rollers otherwise you will wear your chain links hence the more likely hood you will break a chain.