I agree with Phyr, unless you are planning to run a lot heavy Outside attack (Patient/R&G/Princeton) the advantages don't outweigh the costs as JR mainly effects 3 point shots. Long 2s in any offense (outside of Patient really) tend to be forced ones at so you'd rather hae high HND/DR for your big to create good inside shots and force fouls.
That being said, if you have a young player with 6 or 7 JR, training to 10-12 isn't too much trouble and it can be helpful for those few games were you can exploit poor OD bigs.