I use paraffin (with graphite) and I end up riding in the rain or on wet roads every month or so. I seem to get about 5-600 miles between relubing, I haven't really noticed that the water makes much difference. I sometimes lube when it seems like it has been a while and I have a little free time, that way I don't have to listen to the squeaks when it is definitely time to lube!
Off topic, I have found that when I do hear the squeaks, as often as not it is the derailleur cogs and not the chain at all.