Leyrann
Deity
Does extra era points (e.g. max golden era points) cumulate over the next era?
No.
The era score required to get into a dark/normal/golden age for the next era is the score you have the first turn of that era + 12 + 5*golden ages - 5*dark ages + 1*cities for a normal age and another 12 for a Golden Age.
So if you have 3 cities and 24 era points when the Classical Era starts, exactly getting you into a Golden Age (you need 24 points for that), you then need 24 + 12 + 5 + 3 = 44 points for a normal age, of which you need to achieve 20 in the Classical Era.
If you had the same situation but with 32 points, you'd need 32 + 12 + 5 + 3 = 52 points, of which you again need to achieve 20 points in the Classical Era.