Ocean, you don't say if your hives are new or not. If the foundations have been completely drawn out (not likely if they're new this year) then probably no problem stopping. If you have new foundations that the bees are still working on drawing out, personally, I think you're better leaving the sugar water on for a little while. You (us as well) have had a cold spring, and I think alot of blooms are delayed. They will stop taking it when nectar is readily available.
I make my spring mixture 1:1, so I measure out, 5 cups of water, and 5 cups of sugar, 3 cups of water, 3 cups of sugar, ect.