I don't know, you don't have an article idea for ages and then all of a sudden several turn up at once! And, have you noticed that when you have little or no time to write, all your ideas flood out, but when you have all the time in the world to write, you get none! I think that's called Writers' Law!
But don't knock it! Make hay while the sun (sore point at the moment, sorry!) shines as they say. I find that each single article idea can generate at least three spin offs - with a little lateral thinking. You could target three different magazines with one idea that's been tweaked.
Idea: Cake baking.
Spin off 1: Is our obsession with cup cakes fuelling obesity? - for a national newspaper.
Spin off 2: Cup cake baking for the terrified! A beginner's guide to baking the perfect cup cake using your unique flavours - for a cookery magazine.
Spin off 3: The history of the cup cake - for a history magazine or specialist magazine.
You can do this with absolutely any idea you have for articles and the more spin offs you can think of the better! Think of the selling /money making potential you can have if you treble your pitches from one original idea!
Let us know how you get on.