I'm using now 4.6k at 1.315V and have no problems in prime95 in 2 hours. Max temp was 65º Can i run this 24/7 ?
Absolutely. I run 4.6 @ 1.344 (reported, Should be 1.340, but that's what it takes to be completely stable for me) and I have no qualms about running that 24/7 (literally, using the High Performance profile in Windows, except when I'm sleeping, then I just put it in the Balanced profile to let it clock down), so 1.315 is just fine, as far as I'm concerned.
Also, Temps are fine too. I run a degree or two warmer because of the extra voltage, myself (with a Hyper 212 Evo).