Well... sometimes it's possible to get the same response to multiple SVs. It's rare but I've sent 2 visits before and both messages were exactly the same. It was frustrating because he was over 200 miles away but his blue potentials mattered. But yeah I always send campus visits together in one go and it makes no difference in the results of the messages.
As for sending over multiple cycles, I will say that I have heard SVs count for more if you send 10 at once, rather than 3, 3, 3, and 1 over 4 cycles (as an example). The 10 SVs is definitely to pull down recruits, but it's not perfect. Sometimes a recruit will drop after 5-7 visits and sometimes they take 15-20. I probably had about 65% luck with 10 in one cycle, so now I always send 12 and so far it's worked every time. In the past I had a recruit that I sent 10 SV, then 5, then 5 more to finally pull him down. In the end, a DII jumped me and took him away, I didn't fight but he would have been good. Always send a coach call before trying to pull down, the coach will let you know if you have a chance.