[Pathfinder] When is his buff going to run out?

[Arkwright]

I'm currently in a PBP arena-style PVP match against another fellow. He has chugged what I believe is a Potion of Fly and is currently hovering about 50ft above my head, well out of range of my spells and melee attacks.

How can I tell how long his 'Fly' buff is going to last? Can Detect Magic do the job? Spellcraft? Knowledge: Arcana?

What can I do to prepare for future matches where I need to know the duration of an enemy's buff? (Apart from preparing more ranged spells :P )

[jaybird]

Spellcraft to identify spells as they are cast.

[Arkwright]

Does drinking a potion count? Can spellcraft tell me the duration of the spell if so?

[Earthwalker]

As it was a potion you haven't got many options.

A spellcraft would tell you the spell if it was being cast. Then I guess a knowledge local would tell you, your opponents level so you know ow long the spell lasted.

Not sure any rules that will tell you the power of a potion, as it duration depends on the caster level of the potion.