I drafted a SP with the 4th pick, prospective OVR of 89.  He is 18 and has 'probably won't sign' status saying that his dream is to play pro football.  I have been offering him over his demands for the past 2 weeks, 40+ offers.  Each response is the same, "thanks for the generous offer, but he's still contemplating pro football."  Is there any benefit to continually upping your offer to these guys? Or am I wasting my time?

There's never any value in offering more than demands.   Make the initial offer and then wait.  He'll either reject it outright and it'll be done, or he'll come back and say he's willing to play, but the demands will be increased.

Probably won't sign = probably won't sign. Put a milo on him and rank him at the bottom of your list

Yeah, what AlCheez said.  You can only do damage to your prospect budget by offering more.  If he accepts or not has nothing to do with any extra amount offered.

If he rejects the offer, do not delete the email in which he rejects it.  From that email, and only from that email, you will be able to re-make the same offer.  Each time you offer he has a slight chance of signing.