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It all depends on the movement, servicing, etc. If you have a gen Swiss ETA movement based higher end rep, it will last you virtually the same length as the gen itself, as long as you properly service the movement every three to four years. It's easier said than done as full servicing of an ETA auto caliber can be around 150 bucks, and while it's worth it, people just don't think about spending money to upkeep a rep. However, gen watches are based on the same movement, so there really shouldn't be a difference. Breitlings, Omegas, Tag Heuers, IWC, Panerai, all use ETA base movements for most if not all of their watches, which are the same movements inside higher quality reps. That's why paying so high of a price for gens is ridiculous. Rolex, Girard Perregaux, Zenith, Patek Phillipe, etc. have their own "house" movements. ETA is owned by Swatch, and Swatch owns Omega, Hamilton, along with many other Swiss brands. Essentially, buying an expensive rep is like buying a expensive Swatch. In full circle now, if you get an expensive swatch with ETA movement inside, you should be spending 150 bucks every four years or so to upkeep it.
It's like oil change for your car.