As a non-D&D player who is not into the lore, it disturbs me these personality-less non-legendary creatures get the "Elder" typeline.
Lore has less to do here as it does general rules of D&D being placed. Ancient is the 3rd oldest age a dragon can be (in this case 801-1000 years, taken from the Draconomicon that I had to pull off my shelf). I'd call that Elder, personally, but making them the oldest age a dragon can be, Great Wyrm, would have been better to represent that, but it doesn't flow off the tongue as well as Ancient does.
I don't know if the ages have changed in further editions, this is based on the 3.5 rules.
Lore has less to do here as it does general rules of D&D being placed. Ancient is the 3rd oldest age a dragon can be (in this case 801-1000 years, taken from the Draconomicon that I had to pull off my shelf). I'd call that Elder, personally, but making them the oldest age a dragon can be, Great Wyrm, would have been better to represent that, but it doesn't flow off the tongue as well as Ancient does.
I don't know if the ages have changed in further editions, this is based on the 3.5 rules.