I'm not too worried about the peeps figuring where the PCs are going, I'm more worried about them finding the PCs' hideout and storming the place with overwhelming force. It's what they would logically do, the PCs have to sleep somewhere, but if that happens, the PCs are as good as dead. I hate having to rig deus ex machina escape opportunities when the logical conclusion of events would be dead PCs.
I've been giving this matter some more thought.
Let's say a powerful clairvoyant (Level 9) is trying to find the PCs' hideout.
Conventional intel places the PCs in the city. The Peep waits until night since this is when the PCs are most likely to be in the hideout, asleep. He uses a captured possession to focus his talent onto the PCs, and uses Sense in order to confirm the intel (level 1 plus 3 points for Very Distant range (50km) to cover the city and environs) costing 4 points.
"They are in the city - I feel them."
The city centre, as the most logical venue within the 50km range, can be divided into 4 'Distant' (5km) quadrants, and the Peep can check one of them immediately. He has a 1 in 4 chance of finding them in that quadrant by using another 4 points. Otherwise he must wait to recover. So he has a 25% chance of narrowing the search down to Distant (5km) in the first hour.
He requires 3+8=12 hours to recover, so he can't do another search until the next night. Then he can search another 2 quadrants. He has a 75% chance of narrowing the search down to Distant within 24 hours of the start of the search, and 100% in 36 hours.
"They are in the Southeast quadrant."
Next, the Peep tries to narrow the search down to Very Long range (500m). There are 100 VL squares in his Distant range area (10x10). This is a game of Battleships, with the Peep trying to mix Sense with conventional intel to try to figure which 500m square the PCs are holed up in.
On a purely random basis, at two attempts per night, it should take an average of 50 nights, or 6/7 weeks for the Peep to pinpoint the PCs location to Very Long (a couple of city blocks) but with conventional intel helping out and logical weighting on certain areas, this might be significantly reduced.
"They are between Imperial Square and East 57th"
Once the location is down to VL, the next step would be to reduce the range to Medium (50m). This will effectively pinpoint the PCs to a single apartment block. Since this is another factor of 100, it should take the Peep another 50 nights, but I think a conventional door-to-door enquiry across a couple of city blocks would work faster than that.
"They're in the Bayview Apartments."
From here you're definitely on conventional systems - it's much quicker to check the guest book than to Sense every room.
So... On the basis of the above estimations, I'm figuring it should take perhaps 4 weeks or so to narrow the search down enough to find the PCs, most of which time will be narrowing the range down from Distant to Very Long.
Does that sound reasonable?
If so, that means the PCs should move every 3 weeks or so in order to evade discovery.
I'd appreciate comments on this scenario.