There actually is no official spec from AMD yet on the 'MAX' safe core voltage for the FX series Vishera core CPUs. However the consensus among OC enthusiasts is to play it safe and stick with the same voltage limit as with the Phenom II series prior to the FX series: 1.55 vCore max
For 24x7 most will recommend <= 1.475 vCore
So your 1.456 is fine.
If you want to get the most out of it while keeping voltages and temps low, search for and read some good overclocking guides for the FX series CPUs. These have a lot more information on BIOS settings, voltages, stability testing, cooling and temps.