how can you use a long range spell?

[Curmudgeon]

Hmm. If someone isn't trying to hide (say, a group of dumb, angry orcs is charging over the hill), a spot check isn't required, right?

Nope. In D&D 3.5 an encounter doesn't start until someone makes a successful Spot or Listen check (except for forest fires and avalanches, which carry over automatic encounter start rules from 3.0). Those orcs aren't known to you until you hear or see them; of course if they're angry you're probably going to hear battle noises (-10 Listen DC) pretty easily. But the usual explanation is that someone is doing a proper scouting job with a spyglass, or using divination magic so they know trouble is coming. (Also, if you've got the gold, you can get a masterwork 8x spyglass for 16,000 gp instead of the standard 2x model for 1,000 gp.)