The GTX460 is more power efficient and overall better card. On release they said the GTX460 is everything that the GTX465 should have been. All though the GTX465 is more powerful the gap is little. GTX460 is a good overclocker, most of the overclocked cards have better cooling solutions so it is a matter of price premium which one to buy.
It does technically, but its pretty much negligible here.
As long as you keep temps in check, the life of the card would not affect you in anyway. The difference between 10 years and 9 years is negligible, as the cards would be way too slow to run anything worthwhile by then.