With a range increment of 315 using a composite longbow (as a 10th level sniper), and given that projectile weapons can hit targets as much as 10 range increments out, that's 3,150 ft, or 60% of a mile. Of course you'd have a -20 to hit, but I get the feeling that's why the class grants the true strike ability. For that one shot outta nowhere..
Of course, assuming the DC to spot someone is zero, modified by distance, and at -1 per 10 ft. distance, that'd be what? -315 to your spot check to see someone at that range?
Even with my archer's Third Eye: Aware and the Eyes of the Eagle he intends to get combined with cosmopolitan:spot for +2, skill focus:spot for +2, elven racial bonus of +2, and 23 ranks in spot by the time he hits 20th level, that would only be a total +46 to his spot check. Taking 20, he'd get 66, able to spot a foe at 660 feet right?
I wonder if the ability to negate concealment by 30% would apply to not being able to see the target and his effective 50% miss chance for total concealment. It doesn't specifically say the concealment reduction only negates concealment granted by soft cover, and they threw the true strike in there as if anyone will be able to see more than one range increment to need it...