Flashing the BIOS with Skynet allows higher voltages along with the ability to lock the OC clock. Meaning, it's not randomly boosting to wherever it wants. The OC you set, is the OC that it will clock to in all games. Upside is greater stability, downside is higher power usage.
Additional voltage should not affect the life of the card too much. The way I see it, any degradation wouldn't be a problem because I would upgrade the card WAY before it starts to matter. For example, if at stock voltages, the card could last 10 years, but overclocked to the max, it only lasts 8 years. That's perfectly fine to me, because by that time, this card will be ancient history and probably equivalent to what's available in smart phones by then. lol.
Just be aware that higher voltages doesn't always allow higher clocks. You might have just gotten a bum chip that can't go much over stock. Just the way it works out sometimes. Only thing the manufacturer guarantees is that the card remains perfectly stable at default clocks. Anything extra is just a bonus.