With Mann playing as that extra forward in the middle, our forwards aren't really being overworked in relation to the minutes they are playing. Graham and Vaughan are playing about 45-55 minutes each, De Belin 60 minutes, Friz and Sims 80 (most of the time). That's no different to the rotation of every other team. Can't see any reason for a burnout.
Believe me, i've disagreed with Mary's use of the bench for some time.. But it's not as if we're lacking punch in the middle. In fact Mann's impact is becoming more and more immediate. I've seen him poke his nose through a couple of times, and he's acting as a nice little point of difference between Hunt and Widdop.
And to answer your question "do people really believe that is blooding players or preparing them for an 80 minute game in 1st grade come SOO week"... It's not as if we can just drop Aitken, or Sims, or De Belin, or any of these Origin prospects purely because they might get picked and purely to "properly blood" these young players. You still have to pick your best team available, and right now (excluding maybe Nightingale) the current 17 is our best available. What happens if we go with your system of picking them for a game or two and starting them, they have a shocker and then they're dropped back to reserve grade. It's going to shatter their confidence. Sure, it could spark them and they'll want to work harder on their deficiencies, but imagine the backlash on this forum. We're winning, you don't blood youth just for the sake of it. That's what injuries and poor form is for.
Right now, the forwards rotation is working. Lomax is our bench utility and he will come on at the end of the match or in case of injury.