The 300 cycle count lifespan (or 2-3 years, "whichever comes first") was a common thing for lithium-ion batteries until fairly recently, which is probably why beedoola is worrying about it. I think Apple claims that their batteries are good for 1000 cycles now (as do some other makers of lithium-ion batteries); 1000 may be optimistic, but at 300 cycles you still have a way to go.