It appears I have gone through a pair of Fulcrum Racing 5 wheels in 18 months of commuting, based on the advice of Hart's Cyclery. Snapped a spoke yesterday on the way home (first ever), and Hart's basically said that the wheels I was using for commuting were not up to the job, especially as I have a pannier rack, because there are not enough spokes and (I suspect) the side walls are not thick enough. The rims are indeed quite worn, he reckoned I have 6 months left if I'm lucky.
This is the 2nd wheelset I've gone through in 2½ years of cycle commuting around 15 miles a day.
Therefore, what wheelset (700c) do people use for commuting that have 32 spokes and rims that won't get worn through quickly, but ideally don't weigh a ton?