I don’t really worry about tools or actual probability numbers. I do consider that the closer he gets to projected first round, the more likely he is to bump to likely going; which means if he’s going to be under 40, I am likely to just go for it (assuming he has some growth in important areas). I ALWAYS want to avoid ending up with juniors between 30-40. If I don’t think I can keep (or drop) him below 40, I’ll go all in.
Also, if I’ve got his replacement already on my team, I’m less likely to sweat it in any case. Teams do tend to finish the season better when their juniors are fully developed, so I have to figure holding them back does usually cost something, even if it’s hard to see.