There are some technical motivations that may favor moving away from the 2x15 sec snaps per visit to a single 30sec exposure. This would improve readout noise and increase overall survey efficiency by a few percent. However, there are some scientific drawbacks that should be considered.
I started this thread to formulate and discuss the drawbacks and advantages of different snap strategies.
I want to start with two obvious drawbacks:
Saturation limit would be even brighter; time dependent phenomena like planetary transients (including in WFD), microlensing (really only in special programs, but special programs could have different strategies for snaps I assume), stellar variability, and anything that gets bright fast would lose targets or valuable data. Starts studies as well, variable and static. The overlap with some surveys in magnitude range will shrink.
We would lose sub-minute time scales. Right now the 2 snaps could be used to investigate sub-minute timescales and this is relevant for a number of transients, for example CVs. Those times skills would lost (in WFD) and the shortest time scales that could be studied would be ordered one minute in the overlapping regions of consecutive visits