Yeah, I would never fill all 35 prospects. Like I said I only allow 16 at first(my needs) then after a few commit I add more prospects I want.
Your "needs" are the positions that are not completely filled. If you only have 1 HB on your team the CPU is going to tell you that you need 2 more HB's.
Make sure you target at least 2 MLB's and a CB if those are your only needs. I would personally target 2 CB's and 3 MLB's, because theres always that chance that one of those recruits will commit to another school. Then you can go after whatever else you want.
The less prospects you target the more time you will be able to actually call the prospects you need.