Hit places with geo teams as fast as possible, there's nothing to be gained by waiting (So far as I know)
There's something to be gained, but only very little. However, on the other hand, waiting until you've depleted one or more resources is actually a rather bad thing, so I agree that waiting is a bad idea. A geosurvey team's result is essentially a second free survey roll with one extra effect: if you roll a mineral deposit that already exists, you get the *greater* of both amount and accessibility. In essence, you get four conditions:
A. Your geosurvey team comes up with nothing, or comes up with a deposit that has both a smaller amount and accessibility: nothing happens, and you keep the existing deposit.
B. Your geosurvey team comes up with a higher accessibility at the same or smaller amount already on the system. You keep the amount already present with the new, higher accessibility.
C. Your geosurvey team comes up with a higher amount at a lower accessibility (most commonly the infamous 10-million, 0.1 accessibility deposits). You get the higher amount at the accessibility already present.
D. Your geosurvey team comes up with both a higher amount and higher accessibility. You get the newly-found deposit, plain and simple.
The motherlode, naturally, is to combine a high-accessibility, low-amount deposit with a high-amount, low-accessibility deposit; that gives you a high-accessibility, high-amount deposit of the sort Detros posted earlier. Because the amount is replaced rather than added, it can be beneficial to wait to bring in a geosurvey team when your deposits start running a bit low. However, then you run the risk of running the deposit dry, at which point you no longer get to keep its accessibility if you find a large but inaccessible deposit. Plus, it's a bit fiddly to wait; it's simply easier to drop a team on the rock and search right away.
If you make your survey teams survey some of the less worthwhile bodies then it is possible for them upgrade in skill, which in turn could give them an increased chance of having positive results when surveying bodies.
Thankfully, this was changed in 6.0. The only thing geosurvey team skill now affects is the time it takes to complete the survey. You no longer need to worry about wasting your only geosurvey chance by using a low-skill team; you'll just be waiting a bit longer.