Ethereal scouting

[Talisein]

I'm running a group through Second Darkness (currently about to start book 6) and they've developed the strategy of scouting via the ethereal plane. Basically they get to know a spot well, plane shift to ethereal then teleport back to the spot, since plane shift moves them up to 500 miles out. Then they can explore in relative safety for a bunch of clunkers..
I've ruled that peering across the planes is described as indistinct so they can't see creatures moving around, but still gives a big advantage knowing the lay of the land and layout of buildings, not to mention allowing study of areas behind the frontlines for teleport destinations. They've come across forbearance a few times and this could seriously inconvenience them when they meet senior demons with true seeing, but for now it's very, very effective.

It seems like an unusual way to use some relatively big spells to protect the party, so wouldn't say it was broken, but any suggestions for something I've missed or how to manage the effect?

[avr]

They might not get a clear enough view of the material plane to be able to study it for the purposes of teleport. The real thing isn't made of mists after all.

[Moonclanger]

Ethereal scouting (and Astral travel) saw a lot of use when I ran Against the Giants for AD&D. It proved very effective. The party scouted out dungeons one level at a time, then spelled up and took out every monster on the level in one long rolling fight that often lasted 20 to 30 rounds.

It was a lot of fun but it's a technique that can easily ruin an adventure that's not just a simple dungeon-bash. One of the consequences of this campaign was that the GMs in my group decided to henceforth limit the availability of the tuning forks required to cast Planeshift.

[Xenocrat]

That’s what Ethereal Jaunt (scouting) and Etherealness (group scout and ambush) are for.

[Moonclanger]

Xenocrat wrote:

That’s what Ethereal Jaunt (scouting) and Etherealness (group scout and ambush) are for.

Yeah, but they're 7th and 9th level respectively. Planeshift is only 5th level, so you can start doing it at 9th level and with an unlimited duration.

[Cyrad]

Have dangers lurk in the Ethereal Plane. The plane is not totally empty. There's many creatures that live in it. Even one of the official modules has a section where if someone tries to scout a city using etherealness, there will be an army of dread wraiths waiting for them.

Alternatively, have structures that are warded with abjurations effects blocking ethereal creatures or walls that are "dual-aspected" and exist in both the material plane and the ethereal plane.