If you can keep a stony coral alive, you should be ok with a ceph...they are very intolerant of water extremes in ph, ammonia, nitrites and nitrates...so your water parameters have to be spot on !
Most of us over-filter our water to be safe...make sure you invest in a good skimmer and filter system.
As far as longetivity goes, octos are at the bottom of the barrel...most live in captivity for months, some for a year or so...very few for longer than that. They really are "a candle in the wind" so to speak...super neat animals that flare and burn out fast.
greg