It should be noted that the AA 'Spell Casting Reinforcement' and buff duration enhancement focus effects will add to the duration of the spell. This obviously means the spell can scout a much larger area when you have a fair number of AA's and focus effects dedicated to spell duration extensions.
I currently am getting roughly 1 minute and 45 seconds duration, both with the AA previously mentioned and duration-boosting focus effects. And it can go even higher, I figure to around 3 minutes eventually. This 'eye' could travel a pretty fair distance in that time!