[thejeff]

Yes. The ranges are different for different spells, listed in their description, as is their precision modifier.

Mages set to cast spells will only move forward - more accurately default to "Stay Behind Troops" - when they have no valid spells to cast. Once you've got a bit of research done, they'll usually find something to cast: buffs, chaff summons, useless attack spells, something. Only in the very early game when their spellbook is vary limited do they run out. H1 & H2 priests run out of options pretty quickly. Blood mages without slaves can do so as well.

So relying on them to advance is not very useful. Ordering them to move forward is also risky. You don't want them ahead of their blockers or advancing into melee. Probably more important, you've only got 5 script slots. Wasting one on movement means you're one spell closer to the AI wasting fatigue on useless spells. You really want to position your mages at the start where they'll be most effective.

Besides, the ideal situation much of the time is to let them come to you. If you can arrange it so the front lines are clashing within range of your mages and out of range of his, that's perfect. In SP, if I'm not relying on fast elites, sacred cavalry or the like, I'll often position everyone at the back on hold and attack and let the mages buff for a couple rounds before switching to offense.