I've sometimes thought this myself, but then I thought "It's not as if i'm sending them all at once, but after eachother." Much like sending out a ripple which is followed by another, but will get equal enough attention (depending how much effort you put into each, seperate intention).
As for limit? I wouldn't say so, considering that Intention manifestation is a continuous process (which is, by nature, what the subjective mindset embraces. To my knowledge, heh). The only difference now is that you're aware of the process itself.
Happy intending and all that.