Don't be married to full seasons at each level. You have 5 minor league levels, and no matter how patient you are with a guy, he's not going to be improving much by season 5. So if you start him at HiA and promote 1 level/yr, you'll get most of your improvement out of him before he hits the Bigs withour repeating a level. If you start him lower, you can split 1 or more seasons between 2 levels. And it's not a big deal if a guy needs a season and a half at AAA.
The one thing never to do is demote a hot prospect, so don't start him higher than you're going to be comfortable with. There's nothing wrong with starting him at RL and having him touch RL, LoA, and HiA in the same season. There is something wrong with starting him at HiA and then wishing you'd put him at LoA.