I haven't done any overclocking for a while, nor have I done any research on your card (both because I'm lazy) so this is little more than speculation based on experience.
That sounds like a crazy factory OC. You'll get the best out of it by not using 'auto-detect'. Raise each setting slowly and benchmark. Once you start pushing things there's a trade off for stability between memory clock and core clock. You'll get better performance by reducing the core in favour of the memory.
As for temperature, you'll be fine in terms of being able to max-out the card without it frying. IT WILL FREEZE BEFORE IT BURNS.
What will shorten the life of your card is consistently running it hotter than necessary. Ideally only have it running at the faster settings when you need it to be.
If you really catch the overclocking bug, consider bigger heatsinks and perhaps a volt-mod. I had an xFx 6800gt that I could outperform BFG ultras with, saving myself enough for a motherboard.
I wish I had the money to get back into this passtime. I must admit, I envy you