[Greything]

You can go back any time before the final fight as I understand it.

You probably know this already but make sure you keep Kolgan's Horn as the dragon will not come unless you have it.

Ranged weapons and Shale rule here. There are one or two places on the mountain top that the dragon cannot reach except with breath weapons. You will still need to micromanage the fight but find them and it saves a lot of running around.

I tend to do this fight as soon as possible - the loot is not only valuable but is very helpful in other areas.