Who said you have to rest them on the bench? They don't need or shouldn't get any more bench time than other onballers because they can have a strong, even profound influence on the game by resting down back or up forward, depending on their particular skill sets and the team needs at the time. I don't think many modern coaches have thought it through properly yet but Longmire and Worsfold certainly see an advantage and I reckon others will go down that path soon as well.