I have two pokestops accessible from my desk at work, close enough together that when both of them have lures the zones of influence overlap.
Is it beneficial to put down lures on both of these stops at the same time? Will the overlapping area have an even greater chance of spawning pokemon, or will it just be wasting resources on a larger area with the same chances of spawning?
Yes it is beneficial as being in the area of multiple lures increases the rate of which you find pokemon. Some of the places where there are 3 pokestops in the same area are called triple lure setups as there are usually 3 lures running simultaneously.