The Forgotten Realms boxed set also added a couple age categories, doubled the number of attacks, made the breath weapons more flexible, and such. Essentially, it turned the 1e dragons up to 11.Early dragons (1e/B/X): they might look weaker by the numbers, but so were the characters. And they were encountered at much lower levels. A 9th level party could expect to see an ancient red dragon. Breath weapons were 3x a day (so you could do 3 rounds in a row), and they did the dragon's hp in damage. So that ancient red dragon would do 88 points on a failed save, 44 on a made one, each round for 3 rounds. For reference, a 9th level fighter with 16 CON would have 60ish HP, a 9th level MU would have the low 20s in HP.
FR Dragons could use their breath weapon more often than dragons in other settings if memory serves me correctly.The Forgotten Realms boxed set also added a couple age categories, doubled the number of attacks, made the breath weapons more flexible, and such. Essentially, it turned the 1e dragons up to 11.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.